The OP's asking about tritium iron sights...Well, some people like them, some people like Eotechs, some people like Acogs, some people like Aimpoints, so its what you like, or what you get used to as for if they are any good.
The housing is metal.
Trijicon makes a similar one also using fiber optics, but comes in only 2 different sizes of red dot, and they are both huge MOA's. for myself, I prefer a smaller reticle that does not block out a small object at longer range shots.
The Mepro M21 does have smaller red dots, bulls-eyes etc reticles to choose from to fit ones needs better.