Adjustable Fiddle on Slide 74-44Fiddle block on Stainless steel slider. Polyethylene liners ensure smooth adjustability. Delrin(tm) ball bearing sheaves provide a low friction yet strong block. Adjustable screw allows for proper positioning on your track. Works with our 17 68 twin sheet lead car. Track Size 1 1 4" x 3 16" (31 mm x 4. 6 mm), Boat Size 40' 230000 lbs. 800 sq. ft., Sheave Dia. 1 7 16" & 2 1 4" (36 mm & 57 mm), Max Line 1 2" (13 mm), L 5 1 32" (128 mm), W 1 9 16" (40