4 switch modes can control in and out of mode by setting the button so you don't have to worry about pet's safety. It is very easy to install that you only need to tighten the screws and ensure its stability. Made of ABS it is very durable and solid to use. There are three sizes to choose from. It is very suitable for pets including dogs cats rabbits etc. Size Details: S (Outer Size): 20cm x 19.2cm x 1.5cm / 7.87in x 7.56in x 0.59in (Approx.) S (Inner Size): 16cm x 15.7cm / 6.30in x 6.18in (Approx.) M (Outer Size): 20cm x 19.2cm x 5.5cm / 7.87in x 7.56in x 2.17in (Approx.) M (Inner Size): 16cm x 15.7cm / 6.30in x 6.18in (Approx.) L (Outer Size) : 25cm x 23.5cm x 5.5cm / 9.84in x 9.25in x 2.17in (Approx.) L (Inner Size): 19cm x 18cm / 7.48in x 7.09in ( Approx.