KB Performance Pistons, manufactured by UEM (United Engine & Machine), are a line of hypereutectic pistons designed for high-performance aftermarket automotive applications. They are made from a high-silicon 390 aluminum alloy, heat-treated to T6 standards, and feature CNC-machined crowns, high upper ring locations, and other race-ready details. KB Pistons are known for their strength, lightweight design, and ability to handle high compression and heat, making them a popular choice for various performance applications.