The pin that comes with the magloc thumbrest fits on the my TM G17 and on my WE18c. The Competition 2M version has the sides lowered down to the frame leve so it won't impede with the fire selector switch.
here's the thumbrest on my G17:
https://www.dropbox.com/s/5b6fte6si2zxnyf/glock_0.jpg