Material: Aluminum Alloy. Diameter:31.8mm and 34.9mm
Aluminum / Carbon fiber Quick Release Bike Seat Clamp.
Two strong sleek retaining bolts ensure it to be double sturdy and firm.
31.8mm clamp suits for 27.2mm seatpost. 34.9mm clamp suits for 30.9mm and 31.6mm seatpost.
DBLACK34.9:Double bolts&Diameter 34.9MM,SBLACK31.8:Single bolt&Diameter 31.8MM.Please choose what you exactly like.