Through bolt design, 3.250" bore with aluminum caps and steel adjusters. 3.812" bore size is required to run a 40-spline aluminum spool. Weight: 16.2 lbs.  Case includes adjusters, locks, and 7/16" pinion support attachment studs and nuts. This case can be used with 9", 9-1/2", or 10" gears. Installation - Service instructions can be found on Service Bulletin #0001.