This #84 3,500 lb trailer axle spindle is a weld-on spindle with 1 1/2 inch square butt that fits into a section of axle tubing to repair or replace a damaged or missing spindle. This spindle accommodates a 1 1/16 inch outer bearing, 1 3/8 inch inner bearing, and has a 1.72-inch inner diameter seal surface. The square butt spindles will generally fit into round axle tubing, which will generally be 2 3/8 inch diameter on 3,500 lb axles. This spindle specifically would be great for idler axles, or for a trailer that does not need a brake system, as there is no brake flange pre-welded onto the spindle.If you need an accompanying hub for this spindle, you would need our Galvanized 3,500 lb Hub Kit, while if you plan to reuse your existing hubs you will just need a 3,500 lb Bearing Kit. This is a great product for repairing a broken spindle on an otherwise good axle or for building an axle from scratch if you have the experience to make these repairs or fabrications. You will need to use a Spindle Cotter Key to secure the 1" - 14 Standard Spindle Castle Nut (not included) onto this spindle. Specifications- 3500-pound steel #84 axle spindle- Weld-on square butt end measures 1 1/2 inch Diameter x 4 inch Length- 1 1/16" (44649 bearing) x 1 3/8" (68149 bearing) combination- 1.72" Inner Diameter seal surface