The TFO's are both tritium and fiber optic. The light pipes butt up against a tritium vile inside of the sight. Plus the top is partially open to let light in.

And to contradict my original post, the MGW sight tool will work on the SD series front sight if you remove the shim (doh). I didn't even consider that when I installed the TFO's. So it seems like they should call it the MGW M&P and SD sight tool.