I may have the number wrong, but tey wheel set is an early Ultegra. When I bought them I only had 9 speed anything, no way the cassette would go on. I've had several 10 speed cassettes that worked great. I ran them on my 10 speed bike for a year, and just got a new wheel set. My other bike is a 9-speed, so I thought I'd try to play with the 9 speed spacers and see if it will work, as I love the wheel set and it is much better than the current set on the 9-spped bike. I'm going to dis-assemble a couple of 10 speed cassettes and an old 9 spped and see. it may not work, with the difference in the actual gear thickness, but worth a try anyway. I'll post my success or failure. i appreciate the comments.