As with the other Ronstan blocks, Series 50 Blocks incorporate Smart Features with maximum working loads between 1100 and 2640 lbs depending on the block configuration. Sheaves are 50mm (2 inch) precision molded U.V. stabilized Acetal and support a max line size of ½ inch (12mm). The All Purpose (AP) blocks in the 50 Series do not have ball bearings but are extremely durable requiring virtually no maintenance. The pin diameter on the single blocks is 3/16 inch and 1/4 inch on doubles/triples. Use these blocks for mainsheet, halyard, vang and spinnaker control applications on one design keelboats and sportboats to 33 feet. Also ideal for many control lines on larger boats. Ronstan Series 50 blocks are 10-15 percent more compact than other blocks in their class that do not even come close to matching their strength. Smart Features available on the configurations in this series consist of captive lock, swivel, loop, and shackle heads, ringless keyhole becket pins, quick adjusting cleat angles, and rinsing cutouts. Double and triple blocks are supplied with a shackle and have formed loop heads which can be attached directly to a line or attached to a shackle in three different ways.