Knife Switch, Single Pole - Double Throw, Single Pole - Double Throwdurable Plastic Base Knife Switches That Stand Up During Tough Student Use. Poles & Knives Are Made Of Brass For Good Electrical Connections.
Double Convex Lens, Highly polished, optically true lens is excellent for physics classroom demonstrations in optics and light refraction, with ground edges, great for physics classrooms, with highest grade, Size: 100 mm focal length, Lens measures 2in diameter, 0.1 weight