The Mack 57GC387 High Performance Main Bearing Kit is a new old stock product that includes a single crankshaft main bearing. This bearing kit is specifically designed for Mack engines, providing high performance and durability. With the manufacturer part number 57GC387, this kit is a genuine Mack product that ensures quality and reliability for your engine. Perfect for car and truck enthusiasts looking for top-notch engine parts, this bearing kit is a crucial component for maintaining optimal engine performance.