The trigger housing on the right is from a PD trade in Glock 21, the one on the left is to a Glock 21 SF, The one on the right can be modified very easily to fit the Polymer 80 PF45.
What trigger housing do I have?
It is very easy to tell, you place the trigger housing into the rail section from the Polymer 80 PF45, you will see the bottom half sticking out of the bottom.
What a Glock 21SF housing looks like.
How we modify Glock 21 trigger housing.
We use a belt sander from a cheap hardware store, but this could be done with a file or even a sharp knife. All you need to do is remove a little bit of plastic from the rear of the trigger housing.
What it looks like when you’re done.
This is a photo of the modified Glock 21 trigger housing in the Polymer 80 PF45 rail section. Once this is done you can test fit it in the PF45, as long as it fits and there is no more plastic that needs to be removed. Build the PF45, as normal.
What it needs to look like.
This is a modifed trigger housing sitting on top of a Glock 21SF trigger housing.