ShockProof features microscopic solid medium to provide cushioning between gear teeth, while maintaining lower drag For all H-D and aftermarket transmissions This product dampens transmission noise (reducing the notorious shifting clunk found in these gearboxes), dramatically reduces temperature, provides thicker oil films between gear teeth and resists throw-off For all aftermarket versions like Baker, JIMS, S&S, etc. For all H-D trans with Evolution engines, Twin Cam engines, and latest 6-speed Cruise Drive