diff --git a/README.markdown b/README.markdown
index f23efc88..da49afc2 100644
--- a/README.markdown
+++ b/README.markdown
@@ -125,10 +125,6 @@ The author is Alessandro Ranellucci (me).
                             layer with (> 0, default: 1)
         --infill-every-layers
                             Infill every N layers (default: 1)
-        --extrusion-width-ratio
-                            Calculate the extrusion width as the layer height multiplied by
-                            this value (> 0, default: calculated automatically)
-        --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: 1)
       
       Print options:
         --perimeters        Number of perimeters/horizontal skins (range: 1+, 
@@ -168,6 +164,14 @@ The author is Alessandro Ranellucci (me).
         --duplicate-x       Number of items along X axis (1+, default: 1)
         --duplicate-y       Number of items along Y axis (1+, default: 1)
         --duplicate-distance Distance in mm between copies (default: 6)
+      
+      Flow options (advanced):
+        --extrusion-width-ratio
+                            Calculate the extrusion width as the layer height multiplied by
+                            this value (> 0, default: calculated automatically)
+        --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: 1)
+        --overlap-ratio     Overlap between extrusion threads expressed as a ratio over extrusion 
+                            width (> 0, default: 0.15)
 
 If you want to change a preset file, just do
 
diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 321f863e..1dfea977 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -18,7 +18,7 @@ use Slic3r::ExtrusionPath;
 use Slic3r::ExtrusionPath::Arc;
 use Slic3r::ExtrusionPath::Collection;
 use Slic3r::Fill;
-use Slic3r::Geometry;
+use Slic3r::Geometry qw(PI);
 use Slic3r::Layer;
 use Slic3r::Line;
 use Slic3r::Perimeter;
@@ -62,15 +62,18 @@ our $small_perimeter_area   = (5 / $resolution) ** 2;
 our $layer_height           = 0.4;
 our $first_layer_height_ratio = 1;
 our $infill_every_layers    = 1;
+
+# flow options
 our $extrusion_width_ratio  = 0;
 our $bridge_flow_ratio      = 1;
 our $flow_speed_ratio       = 1;
 our $flow_width;
+our $overlap_ratio          = 0.15;
+our $flow_spacing;
 
 # print options
 our $perimeters         = 3;
 our $solid_layers       = 3;
-our $perimeter_infill_overlap_ratio = 0.15;   # factor for flow width
 our $fill_pattern       = 'rectilinear';
 our $solid_fill_pattern = 'rectilinear';
 our $fill_density       = 0.4;  # 1 = 100%
diff --git a/lib/Slic3r/Config.pm b/lib/Slic3r/Config.pm
index 38c531a9..8ae916f0 100644
--- a/lib/Slic3r/Config.pm
+++ b/lib/Slic3r/Config.pm
@@ -115,6 +115,18 @@ our $Options = {
         cli     => 'layer-height=f',
         type    => 'f',
     },
+    'first_layer_height_ratio' => {
+        label   => 'First layer height ratio',
+        cli     => 'first-layer-height-ratio=f',
+        type    => 'f',
+    },
+    'infill_every_layers' => {
+        label   => 'Infill every N layers',
+        cli     => 'infill-every-layers=i',
+        type    => 'i',
+    },
+    
+    # flow options
     'extrusion_width_ratio' => {
         label   => 'Extrusion width (ratio over layer height; leave zero to calculate automatically)',
         cli     => 'extrusion-width-ratio=f',
@@ -125,16 +137,11 @@ our $Options = {
         cli     => 'bridge-flow-ratio=f',
         type    => 'f',
     },
-    'first_layer_height_ratio' => {
-        label   => 'First layer height ratio',
-        cli     => 'first-layer-height-ratio=f',
+    'overlap_ratio' => {
+        label   => 'Extrusion overlap (ratio over extrusion width)',
+        cli     => 'overlap-ratio=f',
         type    => 'f',
     },
-    'infill_every_layers' => {
-        label   => 'Infill every N layers',
-        cli     => 'infill-every-layers=i',
-        type    => 'i',
-    },
     
     # print options
     'perimeters' => {
@@ -371,9 +378,11 @@ sub validate {
         $Slic3r::flow_speed_ratio = $max_flow_width / $Slic3r::flow_width;
         $Slic3r::flow_width = $max_flow_width;
     }
+    $Slic3r::flow_spacing = $Slic3r::flow_width * (1-$Slic3r::overlap_ratio);
     
     Slic3r::debugf "Flow width = $Slic3r::flow_width\n";
     Slic3r::debugf "Flow speed ratio = $Slic3r::flow_speed_ratio\n";
+    Slic3r::debugf "Flow spacing = $Slic3r::flow_spacing\n";
     
     # --perimeters
     die "Invalid value for --perimeters\n"
diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index e5e4a561..50f10f5a 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -1,6 +1,8 @@
 package Slic3r::Extruder;
 use Moo;
 
+use Slic3r::Geometry qw(scale);
+
 has 'layer'              => (is => 'rw');
 has 'shift_x'            => (is => 'ro', default => sub {0} );
 has 'shift_y'            => (is => 'ro', default => sub {0} );
@@ -75,7 +77,7 @@ sub extrude_loop {
     my $extrusion_path = $loop->split_at($start_at);
     
     # clip the path to avoid the extruder to get exactly on the first point of the loop
-    $extrusion_path->clip_end($Slic3r::flow_width / $Slic3r::resolution);
+    $extrusion_path->clip_end(scale $Slic3r::flow_spacing);
     
     # extrude along the path
     return $self->extrude($extrusion_path, $description);
diff --git a/lib/Slic3r/Fill.pm b/lib/Slic3r/Fill.pm
index 57a23e50..545582a7 100644
--- a/lib/Slic3r/Fill.pm
+++ b/lib/Slic3r/Fill.pm
@@ -85,12 +85,12 @@ sub make_fill {
     ])};
     
     SURFACE: foreach my $surface (@surfaces) {
-        my $filler      = $Slic3r::fill_pattern;
-        my $density     = $Slic3r::fill_density;
-        my $flow_width  = $Slic3r::flow_width;
-        my $flow_ratio  = 1;
-        my $is_bridge = $layer->id > 0 && $surface->surface_type eq 'bottom';
-        my $is_solid = $surface->surface_type =~ /^(top|bottom)$/;
+        my $filler          = $Slic3r::fill_pattern;
+        my $density         = $Slic3r::fill_density;
+        my $flow_spacing    = $Slic3r::flow_spacing;
+        my $flow_ratio      = 1;
+        my $is_bridge       = $layer->id > 0 && $surface->surface_type eq 'bottom';
+        my $is_solid        = $surface->surface_type =~ /^(top|bottom)$/;
         
         # force 100% density and rectilinear fill for external surfaces
         if ($surface->surface_type ne 'internal') {
@@ -98,7 +98,8 @@ sub make_fill {
             $filler = $Slic3r::solid_fill_pattern;
             if ($is_bridge) {
                 $filler = 'rectilinear';
-                $flow_width = sqrt($Slic3r::bridge_flow_ratio * ($Slic3r::nozzle_diameter**2));
+                $flow_spacing = sqrt($Slic3r::bridge_flow_ratio * ($Slic3r::nozzle_diameter**2)) 
+                    * (1-$Slic3r::overlap_ratio);
                 $flow_ratio = $Slic3r::bridge_flow_ratio;
             }
         } else {
@@ -107,8 +108,8 @@ sub make_fill {
         
         my @paths = $self->fillers->{$filler}->fill_surface(
             $surface,
-            density     => $density,
-            flow_width  => $flow_width,
+            density         => $density,
+            flow_spacing    => $flow_spacing,
         );
         my $params = shift @paths;
         
diff --git a/lib/Slic3r/Fill/Concentric.pm b/lib/Slic3r/Fill/Concentric.pm
index 2c59e17d..7d1ecd1b 100644
--- a/lib/Slic3r/Fill/Concentric.pm
+++ b/lib/Slic3r/Fill/Concentric.pm
@@ -3,6 +3,7 @@ use Moo;
 
 extends 'Slic3r::Fill::Base';
 
+use Slic3r::Geometry qw(scale);
 use XXX;
 
 sub fill_surface {
@@ -11,8 +12,8 @@ sub fill_surface {
     
     # no rotation is supported for this infill pattern
     
-    my $flow_width_res = $params{flow_width} / $Slic3r::resolution;
-    my $distance = $flow_width_res / $params{density};
+    my $scaled_flow_spacing = scale $params{flow_spacing};
+    my $distance = $scaled_flow_spacing / $params{density};
     
     my @contour_loops = ();
     my @hole_loops = ();
@@ -43,7 +44,7 @@ sub fill_surface {
         my $path = $loop->split_at($cur_pos);
         
         # clip the path to avoid the extruder to get exactly on the first point of the loop
-        $path->clip_end($Slic3r::flow_width / $Slic3r::resolution);
+        $path->clip_end(scale $Slic3r::flow_spacing);
         
         push @paths, $path->p;
     }
diff --git a/lib/Slic3r/Fill/PlanePath.pm b/lib/Slic3r/Fill/PlanePath.pm
index bbb2a564..caf92c94 100644
--- a/lib/Slic3r/Fill/PlanePath.pm
+++ b/lib/Slic3r/Fill/PlanePath.pm
@@ -3,7 +3,7 @@ use Moo;
 
 extends 'Slic3r::Fill::Base';
 
-use Slic3r::Geometry qw(bounding_box X1 Y1 X2 Y2);
+use Slic3r::Geometry qw(scale bounding_box X1 Y1 X2 Y2);
 use XXX;
 
 sub multiplier () { 1 }
@@ -27,7 +27,7 @@ sub fill_surface {
     my $rotate_vector = $self->infill_direction($surface);
     $self->rotate_points($expolygon, $rotate_vector);
     
-    my $distance_between_lines = $params{flow_width} / $Slic3r::resolution / $params{density} * $self->multiplier;
+    my $distance_between_lines = scale $params{flow_spacing} / $params{density} * $self->multiplier;
     my $bounding_box = [ bounding_box(map @$_, $expolygon) ];
     my $bounding_box_polygon = Slic3r::Polygon->new([
         [ $bounding_box->[X1], $bounding_box->[Y1] ],
diff --git a/lib/Slic3r/Fill/Rectilinear.pm b/lib/Slic3r/Fill/Rectilinear.pm
index 639e67be..313b73c7 100644
--- a/lib/Slic3r/Fill/Rectilinear.pm
+++ b/lib/Slic3r/Fill/Rectilinear.pm
@@ -19,7 +19,7 @@ sub fill_surface {
     $bounding_box->[X1] += scale 0.1;
     $bounding_box->[X2] -= scale 0.1;
     
-    my $min_spacing = scale $params{flow_width};
+    my $min_spacing = scale $params{flow_spacing};
     my $distance_between_lines = $min_spacing / $params{density};
     my $line_oscillation = $distance_between_lines - $min_spacing;
     
diff --git a/lib/Slic3r/Fill/Rectilinear2.pm b/lib/Slic3r/Fill/Rectilinear2.pm
index 7d741e65..d8b8f0bb 100644
--- a/lib/Slic3r/Fill/Rectilinear2.pm
+++ b/lib/Slic3r/Fill/Rectilinear2.pm
@@ -3,7 +3,7 @@ use Moo;
 
 extends 'Slic3r::Fill::Base';
 
-use Slic3r::Geometry qw(X1 Y1 X2 Y2 A B X Y);
+use Slic3r::Geometry qw(scale X1 Y1 X2 Y2 A B X Y);
 use XXX;
 
 sub fill_surface {
@@ -16,7 +16,7 @@ sub fill_surface {
     my $rotate_vector = $self->infill_direction($surface);
     $self->rotate_points($polygons, $rotate_vector);
     
-    my $distance_between_lines = $params{flow_width} / $Slic3r::resolution / $params{density};
+    my $distance_between_lines = scale $params{flow_spacing} / $params{density};
     my $number_of_lines = int(0.99999999 + $self->max_print_dimension / $distance_between_lines); # ceil
 
     #printf "distance = %f\n", $distance_between_lines;
diff --git a/lib/Slic3r/GUI/SkeinPanel.pm b/lib/Slic3r/GUI/SkeinPanel.pm
index 06e746c2..1f993df1 100644
--- a/lib/Slic3r/GUI/SkeinPanel.pm
+++ b/lib/Slic3r/GUI/SkeinPanel.pm
@@ -57,7 +57,7 @@ sub new {
         },
         extrusion => {
             title => 'Extrusion',
-            options => [qw(extrusion_width_ratio bridge_flow_ratio)],
+            options => [qw(extrusion_width_ratio bridge_flow_ratio overlap_ratio)],
         },
     );
     $self->{panels} = \%panels;
diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 56ede956..6dcfe94e 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -182,7 +182,7 @@ sub prepare_fill_surfaces {
 sub remove_small_surfaces {
     my $self = shift;
     
-    my $distance = scale $Slic3r::flow_width / 2;
+    my $distance = scale $Slic3r::flow_spacing / 2;
     
     my @surfaces = @{$self->fill_surfaces};
     @{$self->fill_surfaces} = ();
diff --git a/lib/Slic3r/Perimeter.pm b/lib/Slic3r/Perimeter.pm
index 286be429..413f205a 100644
--- a/lib/Slic3r/Perimeter.pm
+++ b/lib/Slic3r/Perimeter.pm
@@ -45,12 +45,12 @@ sub make_perimeter {
             push @{ $perimeters[-1] }, [@last_offsets];
             
             # offset distance for inner loops
-            $distance = $Slic3r::flow_width / $Slic3r::resolution;
+            $distance = scale $Slic3r::flow_spacing;
         }
         
         # create one more offset to be used as boundary for fill
         {
-            $distance -= scale $Slic3r::flow_width * $Slic3r::perimeter_infill_overlap_ratio;
+            $distance -= scale $Slic3r::flow_spacing;
             my @fill_boundaries = map Slic3r::Surface->cast_from_expolygon
                 ($_, surface_type => $surface->surface_type),
                 map $_->offset_ex(-$distance), @last_offsets;
diff --git a/lib/Slic3r/Polyline/Closed.pm b/lib/Slic3r/Polyline/Closed.pm
index c9228782..8d9d54c3 100644
--- a/lib/Slic3r/Polyline/Closed.pm
+++ b/lib/Slic3r/Polyline/Closed.pm
@@ -4,6 +4,7 @@ use Moo;
 extends 'Slic3r::Polyline';
 
 use Math::Clipper qw(JT_MITER);
+use Slic3r::Geometry qw(scale);
 
 sub lines {
     my $self = shift;
@@ -31,7 +32,7 @@ sub is_printable {
     # if no offset is possible, then polyline is not printable
     my $p = $self->p;
     @$p = reverse @$p if !Math::Clipper::is_counter_clockwise($p);
-    my $offsets = Math::Clipper::offset([$p], -($Slic3r::flow_width / 2 / $Slic3r::resolution), $Slic3r::resolution * 100000, JT_MITER, 2);
+    my $offsets = Math::Clipper::offset([$p], -(scale $Slic3r::flow_spacing / 2), $Slic3r::resolution * 100000, JT_MITER, 2);
     return @$offsets ? 1 : 0;
 }
 
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 90b382fb..201e99d4 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -334,7 +334,7 @@ sub extrude_skirt {
     # draw outlines from outside to inside
     my @skirts = ();
     for (my $i = $Slic3r::skirts - 1; $i >= 0; $i--) {
-        my $distance = scale ($Slic3r::skirt_distance + ($Slic3r::flow_width * $i));
+        my $distance = scale ($Slic3r::skirt_distance + ($Slic3r::flow_spacing * $i));
         my $outline = offset([$convex_hull], $distance, $Slic3r::resolution * 100, JT_ROUND);
         push @skirts, Slic3r::ExtrusionLoop->cast([ @{$outline->[0]} ], role => 'skirt');
     }
diff --git a/slic3r.pl b/slic3r.pl
index 1bcddd26..b58dcb18 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -131,10 +131,6 @@ Usage: slic3r.pl [ OPTIONS ] file.stl
                         layer with (> 0, default: $Slic3r::first_layer_height_ratio)
     --infill-every-layers
                         Infill every N layers (default: $Slic3r::infill_every_layers)
-    --extrusion-width-ratio
-                        Calculate the extrusion width as the layer height multiplied by
-                        this value (> 0, default: calculated automatically)
-    --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: $Slic3r::bridge_flow_ratio)
   
   Print options:
     --perimeters        Number of perimeters/horizontal skins (range: 1+, 
@@ -174,6 +170,14 @@ Usage: slic3r.pl [ OPTIONS ] file.stl
     --duplicate-x       Number of items along X axis (1+, default: $Slic3r::duplicate_x)
     --duplicate-y       Number of items along Y axis (1+, default: $Slic3r::duplicate_y)
     --duplicate-distance Distance in mm between copies (default: $Slic3r::duplicate_distance)
+  
+  Flow options (advanced):
+    --extrusion-width-ratio
+                        Calculate the extrusion width as the layer height multiplied by
+                        this value (> 0, default: calculated automatically)
+    --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: $Slic3r::bridge_flow_ratio)
+    --overlap-ratio     Overlap between extrusion threads expressed as a ratio over extrusion
+                        width (> 0, default: $Slic3r::overlap_ratio)
     
 EOF
     exit ($exit_code || 0);