CZ makes both plastic and aluminum... and unless something was off, the ones you got with your P-07 are the plastic ones. They are really great- an improvement IMO over the old SP-01 ones.
s0nspark-I have both the standard P-07 and P-07 UG. I'm not sure but the +2 on the UG sure feels like metal.
Life pretty much sucks now that they're giving away the extensions with the new guns. ...
DOC-From what I'm seeing, only the suppressor ready have the +2 mags.
The plastic ones are $4.99 a pair on the CZ USA website. About the cheapest thing on the site aside from a decal...
Earl-After seeing your post, I went looking on the site and, somehow, stumbled on the Plastic ones but they were $9.99. Even so, I should have ordered them because now, as CZ is "improving" their navigation, I can only find the Aluminum ones for $37.
The magical search phrase seems to be "+2 base pad" ... I had the same trouble finding them when I went back to order ;-)
As for what came on your UG P-07... here is a pic of mine with the plastic +2:

and here is the aluminum one:

Note that on the plastic one on my P-07 there is a "groove" along the side that says "PLUS 2" on one side, whereas the aluminum one is smooth and is more angled at the back. The plastic one also has texturing on the front side similar to the front strap on the P-07. Hopefully that will help you determine what you have. Yours may very well be aluminum ... stranger things have happened! ... but all of the UG pistols I've come in contact with had the plastic ones. FWIW I absolutely prefer the plastic ones to the aluminum... from my experience, they are able to take more abuse without showing it and are much cheaper to replace once they do ;-)
The plastic base pads were on sale a while ago for $4.99 and I bought mine at that price not knowing they were a pack of two. Even at $9.99 they are a good deal unless that is all you are ordering, in which case shipping will tip the scales.