Aluminum, beefy and 5 on 4 1/2" bc. Big bearings, 1.5' and .787" id's. I will bush the Willwood spindle to fit larger Mazda bearings. Wilwood or Speedway hats for 12+" rotors. RX 7 front calipers on rear, possibly Wilwood 4 piston, on front. ateam:thumbup: