I believe the original USP magazines had a hard plastic floor plate. A lot of people complained about them breaking when they practiced a speed reload or shot competition and dropped the magazine to the ground, so for the HK45 and HK45C they went to a rubbery floor plate that doesn't break. Currently the rubbery kind is what's listed on HKParts for both the HK45/HK45C and the USP in .45ACP - magazines are interchangeable in that caliber. You can still buy just the hard plastic floor plate if you want it but it doesn't come with a magazine - you have to buy a magazine with the rubbery floor plate and change out the floor plate.Which models come with the hard and which with the soft?
Some users (I'm one) have one magazine with the hard plastic floor plate from the USP to use as a carry magazine in the HK45C. I prefer it because concealment clothing doesn't snag or bunch up like it can with the rubbery floor plate.