Double ball bearing block with aluminum cheeks and becket. Works with 506-25 or 506-45 for a 4:1 purchase. Delrin(tm) ball bearing sheaves provide low-friction and high safe working load. Swivel head may be locked in place to avoid twist. Sheave Dia. 2" (51mm), Thickness 1 21/32" (42mm), Width 2 1/8" (54mm), Length 6 3/16" (157mm), SWL 1500 lbs. (680kg), Weight 9.1oz (258g), Max Line 7/16" (11mm) Works with 506-97 For boats to 30'