Ok preliminary measurements are as follows: The base that rides against the spur is 28mm in diameter. There is a 1mm lip on the bottom side that surrounds the bearing insert(on the backside but no bearing goes in here) to hold the spur straight. The openings for the bearings are 9mm and in the center 3mm down from the pulley side is a lip to hold the frontside bearing in place,this extends the entire length of the opening as the bearing on the backside of the spur does not go inside the adapter but rather rides inside the spur gear. From pulley side to the rear lip it measures a thickness of 8mm. The pulley itself is somewhat hard to measure but seems to be approx. 6mm wide. I'm sure my explanations are far from perfect so please let me know what else is needed.