CP Piston & Ring Set for Subaru EJ25 WRX STi - Bore (99.5mm) - Size (STD) - CR (10) - Set of 4

CP Pistons is well-known for making strong, reliable forged pistons for performance applications. This set is built for the 2004-2012 Subaru Impreza, specifically for the EJ25 WRX STi engine. If you're rebuilding the top end of your engine or looking to handle more power, these pistons are a solid choice. They come in a standard bore size of 99.5mm and are designed for a 10:1 compression ratio, which is a common target for modified EJ25 engines.

Forged pistons like these are made from a solid block of aluminum that's heated and hammered into shape under extreme pressure. This process creates a much stronger and more durable piston than cast pistons, which are made by pouring molten aluminum into a mold. This strength is crucial for engines that are pushed harder, whether that's through forced induction, higher boost levels, or more aggressive tuning. The standard bore size means they're intended to be used with a fresh cylinder wall hone or a block that has been machined to the original factory specification. The included rings are matched to the pistons to ensure a good seal.

This set includes four pistons and their corresponding rings, ready for installation. Please note that this piston set is not CARB approved and cannot be shipped to California. Always refer to the manufacturer's installation instructions for proper fitment and assembly procedures when working on your engine.