16mm AirBlocks offer very high working loads in an extremely small, lightweight block. These diminutive blocks feature a patented bearing system using stainless balls in a captive, grooved race and provide an honest 250lbs (113kg) safe working load. They are perfect for the new, smaller synthetic control lines found on high-tech dinghies and the obvious choice for competitive racers. 5/8 in LINE, MWL 250#, BS 1200# WT. 7/16OZ SHEAVE 5/8".