Fouriers Mount Seatpost Clamp UL Chain Guide Chain Retention Single Chainring Adjustbale Length 34.9mm 31.8mm Hight Mount Seatpost Clamp Chain guide professional built for MTB Compatible for 34.9mm and 31.8mm seatpost diameter Adjustable design: you can adjust the chain guide the best comfortable length to suitable you chainring ensure your chainring never drop off Easy installation mount on the bike seatpost without dismount you crank We can 100% promise this chain guide is real brand we offer limited life warranty