It's made of high quality low-carbon steel plate or stainless steel, sintered porous bronze as its interlayer and the compound of PTFE material and Pb as its surface. As it is without lead, which makes the bearing lubricating condition cleaner, and in accordance with environmental request.It's based on bronze alloy of a particular formulation with high density with sintered bronze layer as its interlayer, with the compound of mostly PTFE and other factors. As it is without lead, which makes the bearing lubricating condition cleaner, and in accordance with environmental request.