Use cam swivel bases when leads must rotate to face the trimmer; good mainsheet pedestal for dinghies.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.Key FeaturesThe Swivel Base/150 Cam-Matic is the standard configuration with a tall armIdeal for mounting in the cockpit or for use on larger keelboats and small offshore boats that use 7 mm (3.00") plastic blocksHeight: 5 3/4" (146mm)Weight: 13oz. (369g)Minimum Line Diameter: 1/8" (3mm)Maximum Line Diameter: 1/2" (12mm)Fastener Spacing (square pattern): 3/4" (19 mm) centersFasteners: #10 FH (5mm)Fits Blocks: 2.25", 3.00" Light Duty Hexaratchet ,57mm, 75mm Carbo Air Blocks, including Ratchet and Ratchamatic Blocks