Strong and secure mount for your Garmin Varia RTL510, Garmin Varia RTL515, or any other rear-facing device utilizing the Garmin quarter-turn systemATOP dial system quickly and easily adapts with the turn of a dial to fit a variety of seatposts including: 27.2mm, 30.9mm, 31.6mm, D cross-section, or aero cross-sectionThe ATOP lacing system and rubber adapter pad provides a soft interface that wont scratch or wear down carbon or aluminum seatpostsBlackRearMount OnlyUPC/EAN/GTIN: 195893516834