When sourcing custom pistons, you must prioritize material selection, typically 4032 aluminum alloy for street performance (lower thermal expansion) or 2618 aluminum alloy for high-boost racing applications (higher ductility). Key technical parameters include the compression height, piston pin diameter, and skirt profile. Ensure the supplier uses CNC precision machining to maintain tolerances within ±0.005mm and offers specialized coatings like Molybdenum Disulfide (MoS2) for friction reduction or Ceramic Thermal Barriers for heat resistance.