OK. duh...Sorry. It is an Master Airscrew and you are probably right. I think it's an 9x7 or 8. I will double check it and ring back in with an answer. The reason I bought it was to provide additional clearance for the front ski with the trike gear. With the 11x6 props installed I hit a couple of bumps that caused the front ski to rotate too far forward (even with set screws super tight) and broke a couple of props. The shorter 3 blade corrected this problem but reduced thrust significantly.