PFF26-225BLK Upper Engine Mount Insert is made in our hardest Black 95A durometer material for heavily tuned vehicles and track use for maximum strength and response. Designed to fill the voiding in the OE rubber mount, it smooths out gear changes by stiffening and supporting the often perished rubber bush, which is common for failure on tuned vehicles. This will provide a more precise and settled engine response during acceleration and deceleration. A small increase in NVH, usually at idle, should be expected when stiffening the connecting mount between the engine/transmission and chassis. The harder the material used, the greater the NVH transmitted.