They are made from a soft, flexible plastic that is very long lasting and scratch resistant. They can last for years! Each pair is individually sanded on the inside for a smooth finish, and offer a wide field of vision. A thick bungee strap pulled through a small hole in the plastic allows the user to adjust the tension without need to make a knot, just pull to the desired tension and release. This "Friction Lock" is a nice feature, especially for students and tandems where there is a need to change settings often.

Choice of lens color.