Optional accessory for shop's convenience. Place this caster kit underneath the optional waste oil drainage drum for the John Dow oil filter crusher. Allows you to easily roll an oil filled drum around your auto shop rather than manually having to carry it, or lifting it and trasporting with a hand truck. Makes it much easier on your technician's back, and will lead to less injuries and worker's comp. complaints. Pricing is for when purchased with the crusher. Please call us for \pricing when shipped separately.