The Prusa i3 is still very new, and lacked a good single-hotend mount. I designed this mount for the Ubis hot end to work with my self-sourced Prusa i3 using 1.75 mm filament. The Ubis hot end has a groove that is mostly compatible with the J-head, at least according to google searches. This means that this mount should be fully compatible with J-head grooves as well. Included are two hot end mount variants, and a cold end bracket. For the hot end mount, I initially chose the screw hole hot end mount method that most extruders use. However, after reading this thread: http://forums.reprap.org/read.php?1,238528, I decided that a tight fitting groove mount made more sense, and redesigned my mount. Both versions are included. It is possible to adjust the height and depth of the mount, all accessible in the included SCAD files. The cold end mount attaches to the Prusa i3 sgraber frame, and holds the cold end up. I recommend this extruder: http://www.thingiverse.com/thing:34503. For the referenced pneumatic fittings, you should either print that extruder with a 5mm hole, or melt an M5 nut into the cavity. Remember to adjust the filament_diameter to 1.75mm.Hot end mount (groovemount) === BOM: Print the hotend mount with ABS at least 2 perimeters. Do not use PLA! It may soften and lose grip on the hot end. Once it is printed, ream out all the M3 screw holes, and melt the M5 nut into the top of the mount. Screw the pneumatic fitting into the nut. Gently wedge the hot end into the mount. The groovemount plate should gently slide into the groove on the hot end. Align the M3 screw holes, and clamp the groove plate to the mount using the 16mm M3 nuts and screws. Screw the mount into the x-carriage with the 25mm screws. Align the 40mm fan with the two extra holes in the front, and screw them directly into the plastic using 25mm screws. Cold end mount === The cold end mount is meant for the single-plate prusa i3 with the sgraber wings. It should not require any additional hardware. Loosen the top left z-axis smooth-rod holder. Slide the mount over the frame, aligning the holes with the existing screw holes for the z-axis holder. Screw the holder back onto the frame. Clean up the slot for the pneumatic fitting and the M4 screw, then slide the extruder into the mount. Tighten the M4 screw to stabilize it.