I decided to do some modifications to my MKII. The first things ordered were these parts from Tactical Solutions. The Pac-Lite upper is lightweight aluminum with flutes compared to the solid stainless steel bull barrel from the factory. They come with threaded barrels. I got the 4.5" upper and added the red fiber optic front sight and ordered the compensator also. This gun balances to much better now and is considerably lighter. I'm going to get a VQ sear and a Clark bushing next as well as a different set of grips. But here it is so far.