I wrap my coils at 3mm and use a 3/8 I think drill bit to hold it to place it on the head but the STM is pretty easy if you use 26 guage wire it fits between the post and the screw and just bend it a little and tighten the screw. It's made for 26 wire and I use spaced coils which are a little more difficult, I hate doing it but I manage.