A 10mm combination wrench (12 point box on one end, open end on the other) worked well as an adapter for my click type torque wrench. I measured from the center of the box to the center of the square drive when it was in the open end of the combination wrench. I used that length in the formula that came with the torque wrench instructions. The 10mm open end was a good fit on the 3/8" square drive (the spring loaded ball kept things snug). I checked my calculations by linking the setup to an old beam type torque wrench I've owned for years and the torque I was expecting was the one I got.