Our "budget version" of our BMW S65 "Better than Stock" swaps off-the-shelf Mahle 4032 alloy pistons at 92.5mm bore and 12.5:1 compression and Mahle rings and standard pins in lieu the proprietary JE 2618 alloy pistons at 94mm with BMW S62 rings and lightweight DLC pins used in the "high end version." Aside from the reduced bore to accommodate off the shelf piston sizing, the principal difference here is the piston alloy: 4032 is more brittle and less durable than 2618, but 4032 expands less under heat than 2618, permitting closer piston-to-wall tolerances, which in turn minimizes engine noise and oil usage. Also, the ringset is a standard Mahle ringset that comes with its pistons, rather than the race-tested and proven BMW S62 ringset. Rods are upgraded to Carrillo or Arrow. For ordinary street usage, the "budget version" is more than sufficient.  If you plan upgrades or engage in more than occasional track usages, the "high end" version is strongly recommended. Price below does not include $4500 core charge if applicable.  See the Core Charge Policy for details.