Tokico HE2756 HP Rear Shock for BMW 318i/325e/es/is/M3 Piston rod is hardened, chrome-plated and micro-polished for smooth operation and contributing to long seal life Teflon coated piston rod guide minimizes dynamic friction and extends piston-rod life Pressure Tube is mandrel-drawn twice to ensure precise dimensional tolerances and concentricity, for excellent sealing and minimal dynamic friction (drag) Superior ride quality plus shock & strut longevity