The 22/45 versions have an entirely different handle, which is modeled after the popular model 1911, 45 caliber, pistol. The Ruger MK III 22/45 dos not have a cross-pin and uses a different kind of sear spring, so the HSS is not compatible with this model.We plan on developing the Hammer Strut Support for the 22/45 eventually. There are multiple versions of the 22/45, some with and some without removable grip panels and the MK III 22/45 has a completely different sear spring and retention method. Please check back again later, as we do hope to develop the HSS for applicable MK II models with removable grips. This development would perhaps be late 2018.
The MK IV models began to be sold in Dec, 2016. These have a "tip-off" barrel design, wherein the barrel can be rotated off of the frame, after depressing a release button.