This is an eXtreme Heavy Duty caster kit. This is not related to our tubing benders that are xHD capacity, just named similarly. These casters, fixed wheels, plates, and hardware contain everything you need to attach these casters to your existing cart or one you plan to build. The caster plates are made right here in Oregon, the hardware is a blend of domestic and imported, and the casters are imported. Casters feature wheel and rotation locks. Lock mechanisms are NOT the mediocre ones that pivot on the wheel axle and don’t unlock reliably. These are the ones that pivot from their own axle above the tread and are spring loaded and release beautifully. Load capacity is claimed at 500# per wheel by the manufacturer, but these numbers are less reliable brand-to-brand than the numbers published for air compressors, so just know that they are super high quality, double row ball bearing, and about as nice as you can get.