If you own a braze on front derailleur and then purchase a frameset that requires a clamp on front derailleur, this is what you need so you can keep using the derailleur you already own. It transforms a braze on front derailleur into a clamp on style in a matter of moments. You'll need to choose one of three sizes 28. 6mm, 31. 8mm, or 34. 9mm aka 1 18, 1 14, and 1 38 respectively. Two notes of interest: These clamps are 100% compatible with both Shimano and Campagnolo front derailleurs. Also, the 28. 6mm clamp isn't made by Shimano. Shimano doesn't manufacture a 28. 6mm clamp. Rather, it's made by the highly regarded company, Problem Solvers.