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 144 is the standard configuration with a tall arm. It is ideal for mounting in the cockpit or for use on larger keel boats and small offshore boats that use 3.00 in (76 mm) plastic blocks. The low-profile 205 is used when installation is at deck level and when smaller blocks are used. The 1574 accepts Midrange blocks. The 216 features a second cleat for lines led vertically through the base of the swivel. It is frequently used to combine vang or backstay controls in the same swivel base that handles the mainsheet. The 240 and 241 are simple swivel bases for main and jib sheets on very small boats or for control lines on boats of all sizes. The 402 and 403 are fitted with a double cam for use in two-speed mainsheet systems. The 462 swivel base with 338 Micro Cam-Matic� provides precise cleating. The 16 mm sheaves feature low-friction stainless steel ball bearings to handle high loads. Ideal for controls where cleating angles change dramatically.