Act-Mag is the OEM supplier of magazines to Rock Island for their A2 HC pistols with the big magazine well flares.  These pistols use staggered Para-style magazine and are chambered in 9mm, .40 S&W and 10mm.  The magazines come with a unique molded plastic base plate that is tool-less to install and remove.  It is also a one piece unit and does not need a locking plate on the bottom of the spring - instead a plastic "catch" snaps on to the rear of the magazine to hold it in place.

One comment - they fit Act-Mags just fine.  The Act-Mags' bottom feed lips protrude from the base of the mag just enough to let this base plate slide into place and the locking clip pop over the back of the mag.  Mec-Gar brand mags do not have these slightly protruding bottom lips so it takes a small screw driver to help pop the locking clip over the back of the mag.  If you want a tool-less design out of the box with no modifications - only use them with Act-Mags.  

This price is for one base plate - the magazine tubes and other parts are not included.