A recent modification to the RepRap extruder is the addition of two 3mm pins through the clamp and the PTFE insulator to prevent the PTFE slipping out. My PTFE tube is only 12mm diameter compared to the current design which is 16mm so 3mm pins are a bit too big for it. Instead I used some shafts from pop head rivets which are about 2.3 mm.
I drilled the holes 2.2mm to make them a snug fit.
Here are the pins installed through the clamp after being cut to length and rounded of with a grinder:-