These extentions are designed for Vudoo Gun Work's .22lr AICS magazines. I use 10 round polymer magazines, and have not tested them with aluminum magazines. In a 10 round magazine you can load 11 rounds with the loading button installed or 12 rounds with the loading button removed. The button can be removed and installed without dissasembling the magazine.
Everything except the baseplate is reused. This design makes it easy to dissasemble the magazine by pushing the button on the bottom of the magazine into the body of the magazine using a small screwdriver. The extention can then be slid off of the magazine. No modifications need to be made to the original components.
The "Tight" version is a few thou tighter than the other version. This seems to work better with certain types of PLA on my Ender 3.
They are designed to print without supports. I printed them in PLA+. I model in inches, so you may need to scale the .stl after importing it into your slicer. For most slicers, scale to 2540% to convery from inches to millimeters.