diff --git a/bottom.scad b/bottom.scad
index 35aacee..8cb0a18 100644
--- a/bottom.scad
+++ b/bottom.scad
@@ -1,57 +1,13 @@
-$fn = 90;
-
-bumper_diameter = 85;
-body_diameter = 69;
-m3nut_diameter = 6.5;
+include <constants.scad>
+use <cap.scad>
 
 difference() {
 
-    // Cap
-    union() {
-        cylinder(r = bumper_diameter / 2, 
-                    h = 5, 
-                    center = true);
-    
-        translate([0, 0, -5])
-            cylinder(r2 = bumper_diameter / 2,
-                    r1 = body_diameter /2,
-                    h = 5,
-                    center = true);
-         
-        translate([0, 0, 5])
-            cylinder(r1 = bumper_diameter / 2,
-                    r2 = body_diameter /2,
-                    h = 5,
-                    center = true);
-        
-        translate([0, 0, -5 - 7.5]) 
-                cylinder(r = body_diameter / 2, 
-                        h = 10, 
-                        center = true);
-    }
+    cap();
 
     // Make the cap hollow
-    translate([0, 0, -10 + 2.5])
-        cylinder(r = (body_diameter / 2) - 5, 
-            h = 20.1, 
+    translate([0, 0, -1.5 * height_unit])
+        cylinder(r = body_hole_diameter / 2, 
+            h = 4 * height_unit + 0.1, 
             center = true);
-    
-    for(angle = [0, 90, 180, 270]) {
-        rotate([0,0,angle])
-        translate([0, 
-            body_diameter / 2 - 1.8 - 2.5, 
-            -10 - m3nut_diameter / 2])
-            rotate([90, 0 ,0])
-                union() {
-                    cylinder(r = m3nut_diameter / 2, 
-                        h=3.6, 
-                        center=true, 
-                        $fn=6);
-                    
-                    translate([0,0,-3])
-                    cylinder(r = 3.5/2, 
-                        h=6, 
-                        center=true);  
-                }
-    }
 }
\ No newline at end of file
diff --git a/cap.scad b/cap.scad
new file mode 100644
index 0000000..24221d3
--- /dev/null
+++ b/cap.scad
@@ -0,0 +1,80 @@
+include <constants.scad>;
+
+module cap() {
+    difference() {
+    
+        // Actual cap
+        union() {
+            // Bumper
+            cylinder(r = bumper_diameter / 2, 
+                        h = height_unit, 
+                        center = true);
+            
+            // Lower cone
+            translate([0, 0, - 1.5 * height_unit])
+                cylinder(r2 = bumper_diameter / 2,
+                        r1 = body_diameter /2,
+                        h = height_unit * 2,
+                        center = true);
+            
+            // Upper cone
+            translate([0, 0, height_unit])
+                cylinder(r1 = bumper_diameter / 2,
+                        r2 = body_diameter /2,
+                        h = height_unit,
+                        center = true);
+            
+            // End piece that goes into the tube
+            translate([0, 0, -2.5 * height_unit]) 
+                    cylinder(r = body_diameter / 2, 
+                            h = 2 * height_unit, 
+                            center = true);
+        }
+    
+        // Make a grove to slide the tube into
+        translate([0, 0, -2 * height_unit])
+            difference() {
+                cylinder(r = tube_outer_diameter / 2, 
+                        h = height_unit, 
+                        center = true);
+            
+                cylinder(r = body_diameter / 2, 
+                        h = height_unit + 0.1, 
+                        center = true);
+            }
+        
+        // Make the end piece of the cap hollow
+        translate([0, 0, -2.5 * height_unit])
+            cylinder(r = body_hole_diameter / 2, 
+                h = 2 * height_unit + 0.1, 
+                center = true);
+        
+        
+        // Place the nuts
+        nut_y_offset = body_diameter / 2 
+                        - (body_diameter/2 - body_hole_diameter/2) 
+                        + m3nut_depth / 2 - 0.5;
+        
+        for(angle = [0, 90, 180, 270]) {
+            rotate([0,0,angle])
+                translate([0, 
+                    nut_y_offset, 
+                    - 2.5 * height_unit])
+                    rotate([90, 0 ,0])
+                        //This is one nut and the hole attched to it
+                        union() {
+                            cylinder(r = m3nut_diameter / 2, 
+                                h = m3nut_depth, 
+                                center = true, 
+                                $fn = 6);
+                        
+                            translate([0, 0, -m3hole_depth / 2 -m3nut_depth / 2])
+                                cylinder(r = m3hole_diameter / 2, 
+                                    h = m3hole_depth + 0.1, 
+                                    center = true);  
+                        };
+        }
+    }
+}
+
+cap();
\ No newline at end of file
diff --git a/constants.scad b/constants.scad
new file mode 100644
index 0000000..8120d41
--- /dev/null
+++ b/constants.scad
@@ -0,0 +1,25 @@
+$fn = 90;
+
+bumper_diameter = 85;
+body_diameter = 70;
+body_hole_diameter = body_diameter - 10;
+
+tube_outer_diameter = 75;
+
+m3nut_diameter = 6.5;
+m3nut_depth = 3.6;
+
+m3hole_diameter = 3.5;
+m3hole_depth = (body_diameter - body_hole_diameter) / 2 - m3nut_depth + 0.5;
+
+height_unit = 5;
+
+thread_diameter = body_diameter - 10;
+thread_hole_diameter = thread_diameter - 5;
+thread_pitch = 3;
+thread_lenght_top = 12.5;
+thread_lenght_lid = 7.5;
+thread_tolerance = 0.1;
+
+lid_diameter = body_diameter - 5;
+lid_tolerance = 0.1;
diff --git a/lid.scad b/lid.scad
index 0bf3f7e..668a02b 100644
--- a/lid.scad
+++ b/lid.scad
@@ -1,33 +1,39 @@
+include <constants.scad>;
+
+use <cap.scad>;
 use <threads.scad>;
 
 
-$fn = 90;
 
-bumper_diameter = 85;
-body_diameter = 69;
-m3nut_diameter = 6.5;
-
-tolerance = 0.5;
-
-thread_diameter = body_diameter - 10;
-thread_pitch = 3;
-thread_lenght = 7.5;
 
 difference() {
     union() {
-        translate([0, 0, 1.25])
-            cylinder(r = body_diameter / 2 - 2.5 - tolerance, 
-                    h=2.6,
+        translate([0, 0, 0.25 * height_unit])
+            cylinder(r = lid_diameter / 2 - lid_tolerance, 
+                    h=0.5 * height_unit,
                     center=true);
 
-        translate([0, 0, -thread_lenght])
-            metric_thread(thread_diameter, 
+        translate([0, 0, -thread_lenght_lid])
+            metric_thread(thread_diameter - thread_tolerance, 
                             thread_pitch,
-                            thread_lenght);
+                            thread_lenght_lid);
     }
     
-    for(pos = [-15, 15]) {
-        translate([pos, 0, 2.5 + 2.5])
-            sphere(r = 5, center=true);
+    union() {
+        for(pos = [-3 * height_unit, 3 * height_unit]) {
+            translate([pos, 0, height_unit])
+                sphere(r = 1.5 * height_unit, center=true);
+        }
+        translate([0, 0, height_unit])
+        rotate([0, 90, 0])
+        cylinder(r = 1.5 * height_unit, h=6 * height_unit, center=true);
     }
+    
+    
+    
+    //Make the thread hollow
+    translate([0, 0, - 1.5 * height_unit])
+        cylinder(r = thread_diameter / 2 - 5, 
+                h = 1.5 * height_unit + 0.01,
+                center=true);
 }
diff --git a/top.scad b/top.scad
index 421cfb4..cc40424 100644
--- a/top.scad
+++ b/top.scad
@@ -1,75 +1,42 @@
+include <constants.scad>;
+
 use <threads.scad>;
+use <cap.scad>;
 
-$fn = 90;
-
-bumper_diameter = 85;
-body_diameter = 69;
-m3nut_diameter = 6.5;
-
-thread_diameter = body_diameter - 10;
-thread_pitch = 3;
-thread_lenght = 7.5;
 
 difference() {
 
-    // Cap
-    union() {
-        cylinder(r = bumper_diameter / 2, 
-                    h = 5, 
-                    center = true);
-    
-        translate([0, 0, -5])
-            cylinder(r2 = bumper_diameter / 2,
-                    r1 = body_diameter /2,
-                    h = 5,
-                    center = true);
-         
-        translate([0, 0, 5])
-            cylinder(r1 = bumper_diameter / 2,
-                    r2 = body_diameter /2,
-                    h = 5,
-                    center = true);
-        
-        translate([0, 0, -5 - 7.5]) 
-                cylinder(r = body_diameter / 2, 
-                        h = 10, 
-                        center = true);
-    }
+   cap();
 
-    // Make the cap hollow
-    translate([0, 0, -10])
-        cylinder(r = (body_diameter / 2) - 5, 
-            h = 15.1, 
-            center = true);
-    
     // Hole for the lid
     union() {
-        translate([0, 0, 5 + 1.25])
-            cylinder(r = body_diameter / 2 - 2.5, h=2.6,    center=true); 
-        translate([0, 0, -2.5])
-            metric_thread(thread_diameter, 
+        // Actual lid hole
+        translate([0, 0, 1.25 * height_unit])
+            cylinder(r = lid_diameter / 2,
+                        h = 0.5 * height_unit + 0.01, 
+                        center = true);
+        
+        // Add a little bevel to smooth the thread start
+        translate([0, 0, (0.125 + 0.75) * height_unit])
+            cylinder(r2 = lid_diameter / 2,
+                        r1 = thread_diameter / 2,
+                        h = 0.25 * height_unit + 0.01,
+                        center = true);
+                        
+       
+        // Metric Thread
+        translate([0, 0,  - height_unit])
+            metric_thread(thread_diameter + thread_tolerance, 
                             thread_pitch,
-                            thread_lenght, 
+                            thread_lenght_top, 
                             internal=true);
+        
+        // Put a little support unter the thread
+        translate([0, 0, -height_unit])
+            cylinder(r2 = thread_hole_diameter / 2,
+                r1 = body_hole_diameter / 2,
+                h = 1 * height_unit + 0.01, 
+                center = true);
     }
     
-    // Screw holes
-    for(angle = [0, 90, 180, 270]) {
-        rotate([0,0,angle])
-        translate([0, 
-            body_diameter / 2 - 1.8 - 2.5, 
-            -10 - m3nut_diameter / 2])
-            rotate([90, 0 ,0])
-                union() {
-                    cylinder(r = m3nut_diameter / 2, 
-                        h=3.6, 
-                        center=true, 
-                        $fn=6);
-                    
-                    translate([0,0,-3])
-                    cylinder(r = 3.5/2, 
-                        h=6, 
-                        center=true);  
-                }
-    }
 }
\ No newline at end of file