Use cam swivel bases when leads must rotate to face the trimmer. Ball bearing swivel bases feature dual rows of Delrin® ball bearings that swivel freely even under high loads. Bases include stand-up springs and a U-Adaptor to accept a variety of appropriate blocks. The Little Swivel Cam Base is the standard configuration with a tall arm. It is ideal for mounting in the cockpit or for use on larger keelboats and small offshore boats that use 76 mm (3.00") plastic blocks.