The NiteRiderA(R) Adjustable Angle Tail Light Strap Mount was specifically designed for our flagship tail light, the Sentinel. It allows you to fine tune the mounting angle of the light to display the projected Laser Lanes even and parallel on the ground. It&';s an easy on and off non-slip tail light mount that also features a grooved contact pad that makes this the 'go to&'; mount for riders using aero seat posts. FITS A RANGE OF SEAT POST DIAMETERSFits post diameter sizes ranging from 15.8mm - 41.2mm. 27.2mm is the most common seat post size. SYSTEM COMPATIBILITYa Sentinela Solasa Sabrea CherryBomba Vmax+a Omega 330