This is a caster, it comes in black and it is used in conjunction with air conditioners and dehumidifiers. The purpose of this part is to be used as a wheeled apparatus that is typically fastened to a bigger object, and it ranges in size. The caster will allow the bigger object to become more mobile with relatively easy rolling movements....Read more This is an important component of your air conditioner/dehumidifier as it also keeps your appliance stable and leveled, which means it will be less likely to leak water on your floors.