The right size of the gate for the dog is very important. The size is dependent on the size of your pet. If you have a puppy, make sure that you use its adult size of a particular breed as the reference for your height. Do not get a small gate simply because you have a small puppy. If this is the case, when it grows, you will have to buy another set of the gate again. In terms of width, this actually depends on your preference and where you want to place the gate. To be safe, go for the type that has extended features or those that has provision for expansion.