Wilwood's 3" x 42 splined axle mount rotors are manufactured from the same high strength billets with the same precision as our 3 hole mount front rotors. Full symmetrical machining provides perfect balance, perfect flatness and the truest rotation of any aluminum rotor being built. Wilwood's engineered drill pattern combines the highest degree of weight reduction with the highest resistance to thermal distortion in the contact faces. You get smooth engagement and a consistent full pedal from the low knock-back characteristics of this design. A durable black anodized finish prevents corrosion and simplifies the visual inspection of the contact faces. This rotor is .310" thick with a 10.95" diameter.