While the MAD is a nice sight, I would not buy one based on tritium inserts.  The problem is that it is too close to your eye to work. (Same problem with Trijicon A2 aperture with two tritium dots).  

Try this, Take your favorite semi-auto pistol with a three-dot tritium sight setup and shut yourself into a dark room. (After making sure it has no magazine and an empty chamber). Take a sight picture with you favorite stance and notice how you can put the front dot between the two on the rear sight.  Now, hold the pistol in such a way that the rear sight is an inch or less from your dominant eye and try to get that same sight picture.  If you are like most people you will see a front dot and a blur. Not exactly useful, IMHO.

Again, the MAD is a nice sight. I have one on one of my AR's.  Just don't see how the tritium is useful.

Paul
MSTN