Some Options Are : All Plastic, Steel, Fiber Optic, Tritium, Tritium Fiber Optic or Metal rear with front Steel, Fiber Optic, Tritium, Tritium Fiber Optic. Front width of .115, .125, .140 or Fat Dot. Rear width of .140, .150, .180, .200. Depends on your use and sight preference. My favorite for my use is Ameriglo Operator with Trijicon Tritium inserts of green front and yellow rear. Good luck with your quest for the sight that is best for YOU.