The HK45CT accepts 8- and 10-round, double stack magazines. A distinctive feature on the 10-round magazines is an extended floor plate that some shooters call an "elephant foot." Owners of full-size HK45s can use their 10-round magazines in the compact HK45CT.
Like so many pistols of current manufacture, the HK45CT's trigger guard has serrations on the front. I'm not sure of the purpose for this. No conventional pistol grip that I know of utilizes this surface. One excellent aspect of the trigger guard for law enforcement use is that it is large enough to accommodate a gloved finger.
The HK45CT sports three-dot tritium night sights, and they are a vast improvement over the ones atop the full size HK45. Ambient room light, a flashlight, or sunlight can all activate them.
Dimensions of the HK45CT are pretty much what you would expect to see on a compact, concealable handgun. Overall length is 7.91 inches; height, 5.5 inches; and width, 1.5 inches. The barrel is threaded to accommodate a suppressor, 4.57 inches long, polygonal, with a right-hand twist, and a sight radius of 5.58 inches.
An O-ring on the HK45CT gives the pistol a tight barrel to slide lockup. These rings usually last several thousand rounds and are easily replaced.