Part # FF-FL-TN-TP-Plate This is a 1/4" (.250) thick FF & FL Steer and TN & TP Trailer axle plate that can be used to check endplay on an aluminum hub. The steel plate would be bolted to the aluminum hub using the hub cap bolts removed. This bracket is Zinc plated to prevent rusting. Please note that you will need two of these plates to install one on each side of hub to match up to the dial indicator magnets. The hub bolt pattern is drilled for multiple patterns with 5 1/2" and 6 3/4" circle with six 5/16" bolts. The TN trailer hub cap flange is 5 1/2" x 6 bolts and the TP trailer hub cap flange is 6 3/4" x 6 bolts. This plate will also work on the FF steer hub and hub bolt pattern is for a 4-1/2" x 6 bolts. Note; An additional 1/4" hole was added in the center of the plate as a product improvement so you can attached the plates to the dial Indicator.