The HK45 in .45 ACP was developed as an evolution of the USP pistol for the United States special forces. The HK45 full size has the same ergonomics as the P30, while the HK45C has the same ergonomics as the P2000.
The HK45 is overall a smaller and thinner gun than the USP, or at least it’s less bulky. The ergonomics are improved over the USP, but the grip is thinner. This means that the pistol should be easier to conceal but it also results in a reduced magazine capacity of 10 rounds for the full size and 8 rounds for the Compact variation. The Compact, however, will accept longer 10 round magazines.
Both the full size and the compact versions of the HK45C can have their grips customized with larger or smaller backstops in order to accommodate different hand sizes. The HK45 Tactical, or HK45T, and the HK45 Compact Tactical, or HK45CT, come with threaded barrels to add suppressors with high quality tritium front and rear raised sights.