Edit: 09/14/2015 I've added another version of the type C with double fans Works especially well with printrbot simples Edit: 09/10/2015 I've added 2 other versions Version B just has a thicker mouth piece now, From 2.2mm to 2.6mm Version C has taller side covers, Has thicker mouth piece, from 2.2mm to 2.6mm Just slap this on your fins, yo. Fix normals if you have to. Distance between the mouths is 17mm, and 2.2mm thick. Snug fits in between the fins. And if it doesn't, just shim something in there, duh. Stop wasting time and energy trying to re-draw tolerances ya nubs.