16mm Forkhead BlockThe 16 mm is Harken's smallest block. It is perfect for small synthetic control lines found on high-tech dinghies. The patented bearing system uses stainless steel balls in a captive grooved race and has a 250 lb (113 kg) maximum working load.. Specifications:. Sheave: 16mm / 5/8in.. Length: 29mm / 1-1/8in.. Weight: 11g /.38oz. Maximum line: 5mm / 7/32in. Maximum working load: 113kg/ 250lb. Breaking load: 544kg / 1200lb