This ball caster kit includes a black ABS housing, a 12.7mm diameter metal ball, two spacers (1.6mm and 3.2mm thick), and two #2 screw sets.
The total height of this ball caster is 13.5mm with no spacers. You can also adjust the height by adding the spacers.
The ball caster can be mounted to a chassis by the two screw sets included in the kit. The distance between the two screw holes is 14.7mm.