The Allen 20mm Aluminium Sheave Box Dynamic Bearing Sheave is a top-performing solution that enhances the efficiency and longevity of your rigging system. With a convenient detachable axle pin, sheaves can be easily replaced or maintained. The axle pin is secured by the surface on which the box is mounted or the accompanying curved backing plate. This sheave box is ideal for sailboat mast installations, but can also be used on boat decks or other surfaces that require rope or wire passage. Key features include: Sturdy Construction: The body is precision-machined from marine-grade aluminium for lasting durability. Multiple Sheave Options: Choose from three different sheave materials and bearing types to suit your specific needs. Versatile Compatibility: Compatible with a wide range of mast sizes and applications, and comes with a curved backing plate for mounting on a mast's leading edge. Enhanced Rope Protection: Minimises wear and tear on halyards, extending their lifespan. Sheave options include: Ac