This aluminum base pad has the insertion stop position sized to fit the 10 round .45 magazines (TR-10R-45-RG and TR-10R-45-RG-B). It is CNC machined from aluminum billet and will replace the polymer base pads that come installed on the 10R-45 mags.
It can also be installed on any Tripp magazine that has "RG" or "RO" in the part number. I have used them to make up 8 round extended mags for my spare magazines that I carry with my Compact length Kimber. That gives me an 8 round magazines for a reload and the extended stop on the base pad stops the magazine from being over-inserted if I were reloading from slide lock. I just trimmed the top of the stop back until the magazine would lock in and then went another .020" or so.