Original Fat Daddy 510 Connection Tool

Screw the tool into the 510 connector until it stops loosely. Then tighten with the round nut.

To loosen, hold the round nut with a pair of pliers, insert a 4 mm Allen wrench into the top, and turn clockwise a half turn to loosen the lock on the round nut. You should then be able to easily unscrew the 510 tool from the 510 connector.