MW Aluminum through bolt case with steel caps (3.812" bore), lightweight steel spool (40-spline), MW 35-spline pinion coupler, ball / tapered pinion support, 1/2" ring gear bolts, large pinion 9-1/2" 9310 pro gear. All MW Thirdmembers include shipping / storage transporter and 3 quarts of gear lube. (62 lbs) Installation - Service instructions can be found on Service Bulletin #0038.