Antal's OPF range of block are a one-piece aluminium frame with a composite resin fibre sheave. The one-piece aluminium extruded body is the strongest and lightest solution, no assembling pin rivets or screws and nuts. CNC machined - polished - hard black anodized and Teflon coated. The resin (aluminium on larger mod) sheave runs on the main Composite Fibre bearing and on a ground stainless steel hub: low friction high loads - no lubricant required. The self-captive side ball bearing reduces the friction and makes disassembling, cleaning and maintenance very easy. Sheaves are supplied with the stainless steel hub.

The range includes sheave diameters from 50mm to 140mm, in a range if styles including; single, double, triple, fiddle and deck versions, for webbing or shackle connection.

OPF range of blocks with shackle include a swivel head lock, which enables the shackle to attach in two angles (longitudinal or transversal), without swivelling. The single and fiddle blocks can also be fitted with a snap shackle; with a cam cleat available for 50mm, 60mm or 70mm blocks, which is adjustable in 3 positions.