Retains the J-Head groove for mounting to the Kossel Mini Effector
There should be a small gap (.5mm) or so between this piece and the effector so that you can sandwich the top of the jhead into the effector with a compression fit. The top of the part with the groove cut into it is intended to face up and mate with the effector. If you flip the part upside down the gap between the retainer and the effector will be 1.5mm.
I printed at .2mm and its a tight fit, let me know if you need different heights.
NEW: I added a probe version meant to support the end of the allen key probe so it wobbles less.
EDIT 10/28/13: Someone asked so I uploaded a 40mm fan mount I used to cool the jhead.