Bi-metal aluminum alloy, A-Series
.010" undersize
These Sealed Power MA Series main bearings can actually polish the journals on your crankshaft. That's because there's a small percentage of silicon mixed in with the aluminum and tin that make up the bearing-surface alloy. The silicon is there for wear resistance, but its toughness actually smoothes the journals of a crank whose surface hasn't been optimized! This special surface alloy is laid over a high-strength 1010 steel backing and delivers improved seizure and corrosion resistance, as well as better control of wall variance. It also helps to minimize debris embedding, which can score the crank's surface.
