diff --git a/vitamins/shaft_coupling.scad b/vitamins/shaft_coupling.scad
index 9e1a381..105ccf4 100644
--- a/vitamins/shaft_coupling.scad
+++ b/vitamins/shaft_coupling.scad
@@ -20,7 +20,7 @@
 //! Shaft couplings
 //
 include <../core.scad>
-
+use <../utils/tube.scad>
 
 function sc_length(type)       = type[1]; //! Coupling length
 function sc_diameter(type)     = type[2]; //! Coupling outer diameter
@@ -31,9 +31,9 @@ module shaft_coupling(type, colour = "silver") { //! Draw the shaft coupling
     vitamin(str("shaft_coupling(", type[0], "): Shaft coupling ", type[0]));
 
     length = sc_length(type);
-    diameter = sc_diameter(type);
-    d1 = sc_diameter1(type);
-    d2 = sc_diameter2(type);
+    radius = sc_diameter(type) / 2;
+    r1 = sc_diameter1(type) / 2;
+    r2 = sc_diameter2(type) / 2;
 
     grub_length = 3;
     module grub_screw_positions() {
@@ -42,7 +42,7 @@ module shaft_coupling(type, colour = "silver") { //! Draw the shaft coupling
             translate_z(z)
                 for(a = [0, 90])
                     rotate([-90, 0, a])
-                        translate_z(diameter / 2 + 1)
+                        translate_z(radius + 1)
                             children();
     }
 
@@ -50,16 +50,9 @@ module shaft_coupling(type, colour = "silver") { //! Draw the shaft coupling
         render(convexity=2) difference() {
             union() {
                 translate_z(-length / 2)
-                    linear_extrude(length / 2)
-                        difference() {
-                            circle(d = diameter);
-                            circle(d = d1);
-                        }
-                linear_extrude(length / 2)
-                    difference() {
-                        circle(d = diameter);
-                        circle(d = d2);
-                    }
+                    tube(radius, r1, length / 2, false);
+
+                tube(radius, r2, length / 2, false);
             }
             grub_screw_positions()
                 rotate([180, 0, 0])
@@ -70,4 +63,3 @@ module shaft_coupling(type, colour = "silver") { //! Draw the shaft coupling
     grub_screw_positions()
         not_on_bom() screw(M3_grub_screw, grub_length);
 }
-