The shells are riveted into place, they are not intended to be removed...I have made them in the past for folks who wanted them removable but omitted the stitching around the kydex.... reason being not each shell is the same size.
The reasons I rivet are many but for one it does not bulk the overall size of the holster for a one size (or a most size) fits all scenario.
Another reason is if its removable you need a lot of larger fastners on the back of the holster for the on and off game with shells, thus you kinda' defeat the whole reason for comfort.
There are several ways to make kydex shells, some folks use a cnc router and a vacuum table and churn them out to get most sizes to fit one possible external shape, so some kydex shells are going to be BIG for a smaller firearm while some look proportional for the size but thats the sacrifice you make when making swappable shells.
I like to keep them in proportion to the size of each firearm, thus the reason I hand make each one.
I hope this helps!
All the best!
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