Cat Mate / Dog Mate pet doors are plastic framed with a self-liner that serves to 'frame out' a hollow core door. The liner also makes for a neater appearance in a solid core door.

The flap is a rigid acrylic with weather strip around the perimeter and seals quite well.  The Small/Medium size is actually marketed by Cat Mate as 'Small Dog' size. Previously they called it 'Large Cat' size and both descriptions are appropriate. That particular size incorporates a "4-way" locking mechanism as does the small '4-way' shown.

Dog Mate 216 Door Mount - Large Size

CAT MATE

#216 Parts