I got one to try with my Mark 23. It's not very good. Won't insert on a closed chamber fully loaded. Not easy to insert on closed chamber period. It's a real pain in the ass to load the last few rounds without a speed loader. Mine got a nick in the metal at the top that bound up the follower on it's first trip out to the range. Slide locked back with a single round in the mag, it won't close by racking the slide. Noticed this since the last time I shot with it, I suspect this means it might lock back on the 2nd to last round instead of empty. That sleeve that comes with it is for the USP 45 and doesn't fit (I knew that beforehand though).