Initial purchase did not meet expectations. I filed down the protruding key to fit my 1/2' diameter pully. The 10mm shaft had a flat which accommodated the shaft adapter to slide on the shaft. However when the adapter was forced on to the 10mm shaft, it made the outer 1/2' adapter diameter larger, and it would not allow the pulley to fit. I purchased the following item instead (am-0333 1.152 in. ID 0.442 in. OD 0.5 in. Brass Spacer) which provided the necessary difference in the 10mm shaft to the 1/2' pulley. I am thankful that both parts were available from Andymark, and thankful too for their prompt delivery.