These axles are designed specifically for off-road enthusiasts to economically upgrade from a conventional truck floater to a bulletproof 40-spline floater setup. This assembly includes through-hardened and polished 4340 axles with a "donut" spline adapter and cover that are made to fit a 2005 - 2010 OEM F350 unit hub. MW donut spline adapter’s splines are manufactured with a slight crown that allows some misalignment without bowing the axle shaft. (This bowing creates forces on the center section that will eventually destroy gears and bearings.) Axle splines are true involute. The center section spline is available for any spool / carrier requirements. Axles made from 4340 material. Covers are anodized aluminum with low-profile sealing o-rings. Gun-drilling is available for up to 37" long with a 7/8" hole. Weld cups for the hub are available for 3-1/2" (p/n 50290) and 4.00" (p/n 50295) housing tubes. Install appropriate weld cups, and download Service Bulletin #0100 axle order form to help gather your dimensions. Installation instructions can be found on Service Bulletin #0102