Captive liners allow blocks to glide along the track virtually without friction, yet they handle up to 3,500lb. of tension or compression load. They swivel 45 to each side of the track and their patented design prevents blocks from hitting the deck when sheets are flogging. For sails up to 715 sq. ft. and boats to 38'. Bearings: Plain bearing Shackle/Strap Type: 45 stand-up-spring shackle on T-Track slider Configuration: Genoa lead block, 1" or 1-1/4" T-Track Features: Lined low-friction slide with spring-loaded pin