This extruder is based on flintsaint, but then i make my self, with same way to extrude filament. This use MK8 and 2x624 bearing. For the loop back, use PFTE with M5 nut put on the Lock so easy to insert. For the spring, i use a circle metal from JEPIT BUAYA. The main object is symetric, so you can just print with option mirror object (in repetier). If you dont want to use double grip, its fine, just dont loop back the filament, and it become standar one way extruder.2x 624Bearing 2x M4 Bolt (cut if necessary) 3x M4 Nut 2x M3 (10mm) and washer Metal from Jepit Kumbahan... (please google, you will know it) Print Part 1 and Part Lock , then print part 1 mirrored.