I have installed 3 Kart EZ fit barrels on my guns. All 3 lock up tight with no movement in any direction. The outside dimensions of the bushings are slightly oversized and had to be taken down to fit the slide.
The lower lugs and standard link are fitted from Kart and the lugs rest tight on the slide stop pin.
It is a good idea to get the Easy Fit Tool Kit. It includes a file, feeler guage, bench bushing and barrel locating block. The directions are very good and informative.
Go slow and use a black or blue marker to see where the barrel touches or rubs and a very small amount of metal can be removed. When I got close to the final fit I felt the file was too aggressive and used a polishing stick. It takes a few hours to complete. After the barrel was fitted I polished the entire barrel. Kart bead blasts the barrel and it has a dull finish.
Good Luck, Ed.