Self-Lubricating THRUST WASHERS – INCH • Carbon Steel Backing • Self-Lubricating Liner • Maintenance-Free NOTE: A composite liner consists of a carbon steel backing, an intermediate layer of sintered bronze, PTFE, and lead sliding lining. The bushing contains a certain quantity of lead which, owing to wear during operation, is gradually released and may mix with the products being manufactured. The quantity of lead released is minimal and does not normally exceed a few parts per million (ppm).