We purchased 3 of the extra large doors more than 4 years ago and they've worked perfectly for us.
We have an odd configuration, hence needing 3 doors, so the dogs go from laundry room into garage, from garage into workroom, workroom to outside in back yard. All of the doors have functioned perfectly.
We now have 4 dogs ranging from a 75 lb hound mix, to a 14 lb Pom/Chi mix and none of them have issues going through the door. Sadly, our 120 pup, the one we needed the extra large door for, passed away 2 years ago. But I love the extra large size.
We recently adopted a very, very frightened Pit Bull. He is afraid of everything that makes noise, that included the "swoosh" noise of the doggie door. But after just a couple of weeks he got the hang of it and uses it now like he's been doing it all his life.
The insert in the door to the outside is finally showing wear and letting in cold air, so I'm looking to replace either just the plastic insert, or the whole door if I can't get just the plastic, but we'll definitely stick with this brand.
We have been pleased from day one with these doors. And the fact that we have 4 VERY active dogs who barrel through them, plus 5 grand-dogs who visit for dog parties, I can tell you, plastic or not, these are very well made doors. Don't be fooled by the plastic construction!
I highly recommend these doors. With proper installation, they'll last you quite a while and are well worth the cost.