73-45 Reefing slide/block allows the "dead end" of the reefing line to be tied or spliced and led around the boom and through your clew reefing grommet. Slide features our polyethelyne liner for easy adjustment on 1-1/4" t-track. Works for most mainsails for boats to 40'. Track Size 1-1/4" x 3/16" (32 mm x 5 mm), Boat Size Up to 40' (12.0 m), Bail Width 13/16" (21 mm), Bail Height 1-3/16" (30 mm), L 3-19/32" (91 mm), W 3" (76 mm), H 1-5/32" (30 mm), Weight 8 oz. (227 g)