This F9 4130 chromoly housing includes our completely TIG welded fabricated housing center that features a 3/16" thick chromoly steel body, a 3/8" thick chromoly steel 3rd member mounting face (that is notched for use with 10" ring gears), and 4 1/2" x .3125" wall 4130 chromoly tubes installed (optional .188 wall tube for super light housing). Housing is custom built to your overall width and pinion offset specs. (up to 66" wide - additional width at extra cost). Unique to this design, the first bend in the fabricated housing center is centered with the center line of the axle tube. This allows the bend to be the point of lowest ground clearance, and the flats on the housing to provide maximum ground clearance at up to 20 degrees of pinion angle! Another unique feature are the welded in bulkheads inside the housing center that tie the face, the body, and the inner ends of the tubes all together. We machine a flat on one side of the inner end of the tube which allows it to key into the inner bulkhead before welding. Arguably the strongest fabricated housing design to ever hit the market!