Perrin Polyurethane Transmission Mount Subaru WRX & STi 2015+ Why do I Want Stiffer Transmission Mounts? Stiffer transmission mounts give you a more connected feel with your car. The PERRIN Transmission mount kit will reduce most drivetrain movement, which efficiently transmits more power to the ground. This means more accurate launches during drag racing and Auto cross type events where you do not want drivetrain slop. Design: The PERRIN Transmission Mount uses custom made large diameter 70a Durometer polyurethane bushings which are pressed into CNCed aluminum mounts, held in place with large bolts and a thick steel base plate. The larger bushings allow the extreme vibrations and sounds to be absorbed, while keeping the transmission from severely moving around under extreme loads. Another feature the PERRIN Transmission mounts have a proper interlock built into it. The stock part is held together with bonded rubber and a couple of small tabs, which means it is possible that the OEM part could fail and leave your transmission disconnect from your chassis. Construction: The PERRIN Mounts are made from CNCed 6061-T6 aluminum, formed powdercoated steel and custom made polyurethane bushings. Because these mounts are stiffer than your stock transmission mounts, there will be some added NVH (noise, vibration, harshness). The noises can be described as more gear whine coming through the chassis. For most people this is pleasing, feeling your engine solidly connected to the chassis, versus having that sloppy disconnected feel.