This is a good cat door,      and offers good value for the money. It uses a small magnet in the collar that is detected by an electronic sensor when your pet gets within about 12 inches of the door. The lock secures the door in both directions, where most other doors do not.  The electronics really work.  There are a number of cheaper “magnetic” latch doors that really don’t work all that well because the pet’s collar magnet has to be within a fraction of an inch from the sensor – a task that’s very hard to train for.
 
The door is only available in one size, which works for cats and small to medium dogs. If you have a medium dog, be sure to confirm the opening 8.5” wide by 11” high will be large enough. PetSafe       indicates it’s for pets up to 100 pounds, although large dogs will likely be too big.

The door itself is made of a flexible plastic (not good), but is strengthened with two side strips of hard plastic on the sides and on the bottom (better). Without a raccoon problem, the door will hold up well. We’ve gone through two flaps after raccoons ripped the door apart breaking the hard plastic that’s mounted on the flap. On the second door, we replaced the plastic with flat aluminum stock, which then withstood further attacks.  A neighbor with the same door had the same problem.

The body is made of white hard plastic and is constructed well. There are controls at the top to turn it on or off, or set one of three states – locked, unlocked, or automatic (i.e. locked until the pet gets near the door).  It also includes a low battery indicator.  I got about 8 months of use on a fresh set of batteries. It requires 4 D cells.  Note that you can’t install this in a metal door as it will interfere with the electronic detector.

If you have multiple pets, additional collars are cheap.  The PetSafe collar is a good design and is easy to adjust. It also appears the magnet design has improved in the last couple of years, as the older ones were big and could dig into your pet’s neck.  Note that this design is not keyed, and if there are other pets in the neighborhood that use magnets in their collars, the door will open for them too. This is not that big a concern for most people.