16mm Double Plain Bearing Block With Acetal Sheave. Designed to be lightweight and cost-effective. Ideal for low loaded systems, such as control line bungee take-ups or rope guides. Plain Bearing Ð The acetal sheave spins around the central axle. This type of bearing has a long lifespan and is very low maintenance.Lightweight Strap - The body of this block is formed in stainless steel for a lightweight yet robust frame.