Got a Pelican 1720 with no middle foam in it. Hoping to buy some replacements and cut them out for a bunch of different rifles, but is the material/quality/dimensions the same for all the pelican replacement foams advertised on Amazon or even eBay? The 3 pack sets... Are they all the same size? Middle foam is the same as the top and bottom foam for dimensions?
No clue about foam tech so I just wanted to make sure everything is good to go.

Generally foam is foam.  I recommend the picknpluck.

Pelican foam for a case is in three pieces:

1) a convoluted (egg-crate type) for the lid

2) a thick (about 2 inches) for the middle (this is the section that is cut)

3) a thinner (half-inch thick) bottom piece.