diff --git a/scad/gears/polygroove.scad b/scad/gears/polygroove.scad
index 783ac4b154c19bb68f9e1b9fcdedc814019cb513..ac7a9dc52fedd20c19fec8ca806f406276c36d49 100644
--- a/scad/gears/polygroove.scad
+++ b/scad/gears/polygroove.scad
@@ -121,13 +121,26 @@ module PolygrooveBeltInner(diameter, angle=360, teeth=5, grooveWidth=3, grooveDe
     translate([grooveDepth/2 + diameter/2, 0, 0])
     mirror([1, 0, 0])
     PolygrooveBeltProfile(teeth=teeth, grooveWidth=grooveWidth, grooveDepth=grooveDepth, flattenTeeth=flattenTeeth);
+}
+
 
+module PolygrooveBeltOuter(diameter, angle=360, teeth=5, grooveWidth=3, grooveDepth=3, flattenTeeth=0.3) {
 
+  assert(diameter > grooveDepth/2, "TODO: msg!");
 
+  rotate_extrude(angle=angle)
+    translate([-grooveDepth/2 + diameter/2, 0, 0])
+    PolygrooveBeltProfile(teeth=teeth, grooveWidth=grooveWidth, grooveDepth=grooveDepth, flattenTeeth=flattenTeeth);
 }
 
 
-PolygrooveBeltInner(diameter=70, angle=97, teeth=5, grooveWidth=3, grooveDepth=3, flattenTeeth=0.3, $fn=100);
+PolygrooveBeltInner(diameter=70, angle=90, teeth=5, grooveWidth=3, grooveDepth=3, flattenTeeth=0.3, $fn=100);
+
+
+translate([70, 0, 0])
+  rotate([0, 0, 180])
+  PolygrooveBeltOuter(diameter=70, angle=90, teeth=5, grooveWidth=3, grooveDepth=3, flattenTeeth=0.3, $fn=100);
+
 
 
 // ⬇ Example code below ⬇