Our skimmer appears to have a liner in it. Is that a thing? When I look at others online, I don't notice anything like this - but it's difficult to tell from pictures. It's not covering the whole interior; but rather begins approximately 4" past the faceplate and goes all the way to the basket. I noticed early on that it appears to be breaking down. There are bubbles in it, and I've pulled a few pieces out of the skimmer basket as well as the pump strainer on startup this year. What's left peels away easily.
My instinct is to tear the rest of it away to keep it from clogging plumbing. I notice there is plastic beneath that seems to be the same as the rest of the skimmer body, so I'm not sure of any function it could be serving - but also don't want to inadvertently blow my pool up.

Please excuse the dirt and grime in the photos - I'm cleaning it as well as I can from outside the pool and working towards being able to get in there to brush this thing out properly.
Second, my skimmer does not have a weir door. I don't see any notches for one, but it looks as though some are made universal. Besides measuring for the proper width, are there any other considerations I should make before trying to buy one and install it?
Thanks in advance for any insights!
My instinct is to tear the rest of it away to keep it from clogging plumbing. I notice there is plastic beneath that seems to be the same as the rest of the skimmer body, so I'm not sure of any function it could be serving - but also don't want to inadvertently blow my pool up.


Please excuse the dirt and grime in the photos - I'm cleaning it as well as I can from outside the pool and working towards being able to get in there to brush this thing out properly.
Second, my skimmer does not have a weir door. I don't see any notches for one, but it looks as though some are made universal. Besides measuring for the proper width, are there any other considerations I should make before trying to buy one and install it?
Thanks in advance for any insights!