Top plate is 5/16" cold forged. Top plate measures 4-3/4" x 6-5/8", bolt hole is 2-7/16" x 4-15/16", slotted to 3-3/8" x 5-1/4". Features precise double ball bearings. 3/4" Kingpin. Roller bearing. Zinc plated. FOB Shipping Point. Steel surcharge may apply. Wheel Description PAYRON - Cast iron steel. BRONCO - Gray rubber, Alum center. PAYTHANE - Red 95 Poly, metal center. PLEXITE - Black phenolic.