"The RAM Torque Rail Base accommodates rails and bars ranging from 1.5"" to 2"" in diameter the perfect mounting solution for your ATV or UTV. The include B size hex ball adapter can connect to either side of the Torque base, and is suitable for rugged environments for supporting action cameras, spotlights or other devices. Two sizing inserts one for attachment to 1.5"" rails and the other for attachment to 1.75"" rails are included to create a tight hold while nylon-insert locknuts prevent loosening in high-vibration environments. Available separately, the RAM B Size Ball Add-On allows you to attach an additional B Size Ball to the Torque Rail Base for mounting multiple devices."