Knife Switch, Double Pole - Single Throw, Double Pole - Single 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: 200mm focal length, Lens measures 3in diameter, 0.2 weight