Single 12 Series Block with UC Ball bearing sheave. Powerful 4" (102mm) sheave diameter runs on Nomex(tm)/Teflon(tm) composite bearing and twin ball bearing races for maximum thrust load capacity. Stainless Steel cheeks are reinforced for high loads. Swivel head "D" Shackle may be locked in place. Bolted construction allows for disassembly and proper maintainence. Length 8-9/32" (210mm), Width 4" (102mm), Thickness 1-1/2" (38mm), Weight 2lbs 13 oz (1.28kg), Maximum line diameter 3/4" (19mm), Pin diameter 7/16" (12mm), Safe Working load 5000 lbs (2270kg).