These weld-on top plates are specifically designed to fit our medium-duty industrial series casters, making them perfect for attaching casters to steel equipment. All you have to do is weld on the top plate, paint it, and attach the caster. Our medium-duty industrial series casters match perfectly to the bolt holes on these top plates. When attaching the casters, make sure to use 3/8″ attaching bolts. These top plates are also compatible with our medium-duty industrial series floor locks.