4 switching modes can be controlled with one adjustment knob, so you don't have to worry about your pet's safety. Installation is very simple , just tighten the screws and make sure it is stable. Made of ABS, it is very durable and sturdy to use. Available in three sizes . Ideal for pets including dogs, cats, rabbits and more. Size details: S (external dimensions) : 20cm x 19.2cm x 1.5cm / 7.87inch x 7.56inch x 0.59inch (Approx.) S (inner size): 16cm x 15.7cm / 6.30in x 6.18in (approx.) M (external dimensions): 20cm x 19.2cm x 5.5cm / 7.87in x 7.56in x 2.17in (approx.) M (inner size): 16cm x 15.7cm / 6.30inch x 6.18inch (approx.) L (external dimensions): 25cm x 23.5cm x 5.5cm / 9.84inch x 9.25inch x 2.17inch (approx.) L (inner size): 19cm x 18cm/7.48in x 7.09in (approx.) XL (external dimensions): 22cm x 25cm x 5.5cm (approx) XL (inner size): 22cm x 20cm (approx) Size: S, M, L, XL (optional) Color: Black, White (optional) Packing List: 1 Pet Door 1 x set of mounting screws