Plain Bearing RWO's plain bearing blocks for wire, all have metal sheaves. The 18mm (11/16ins) are brass whereas the 25mm (1in) and 38mm (1.1/2 ins) are anodised high grade aluminium with a plastic bush. The bodies and axles are all stainless steel, Designed for wire halyards and control lines with numerous configurations and three sheave sizes. Cascade Vang Systems The more powerful racing craft now tend to use multi-purchase (up to 24.1) cascade systems to flatten the sail or re-shape the mast. These should be based on our Hi-performance ball blocks or carbon sheaved blocks to handle wire or the latest "state of the art" line such as Spectra�, Vectron� &. Zylon�.