Part No. 421 The 16 mm is Harkens 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. Sheave (mm)16 mm Sheave (in)5/8 in Length (mm)60 mm Length (in)2 3/8 in Weight (g)18 g Weight (oz).63 oz Maximum line (mm)5 mm Maximum line (in)7/32 in Fasteners (mm)4 RH mm Fasteners (in)#8 RH in Cutout (mm)11 x 35 mm Cutout (in)7/16 x 1 3/8 in Maximum working load (kg)113 kg Maximum working load (lb)250 lb Breaking load (kg)544 kg Breaking load (lb)1200 lb