Fastace Fsp-503 Mountain Bike Hydraulic Dropper Adjustable Seat Post Lower Holder Remote Lockout Tube 31.6 mm 1436-1438 Holder type: Lower Suitable seat tube inner diameter: 31.6mm Length & travel: 440mm-125mm Adjustable by manual and remote control 170 MM Cable & Internal Cable Routing please make sure your bike frame design is suitable for this holder type