Hook-Type Sheave 4,000 Pound Capacity. 18" (457.2 mm) hook sheave with 7" (177.8 mm) minimum radius. Strong, welded steel frames. Forged steel closure-type hooks with 1" (25.4 mm) opening. 5" (127 mm) wide aluminum alloy sheaves with self-lubricating bearings. Select a sheave with a maximum rated ca