The Wimberly Sidekick Sk 100 is a gimbal head that has a built-in Arca-Swiss style quick-release clamp.  The gimbal is a lightweight and portable tripod accessory that allows you to attach a lens to the gimbal that, in turn, attaches to your ball head for fast moving photos such as wildlife and sports.  In order to use the head, your lens must be equipped with an Arca-Swiss style lens plate (not included).