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: 200 mm focal length, Lens measures 3in diameter, 0.1 weight
ultrasonic Probe, Dimensions: 65 mm X 27 mm Dia, For Use With ultrasonic Echoscope, Includes A 16-mm Piezo-Ceramic Disc In A Die-Cast Metal Case And A 1-M Long Cable With A Frequency-Coded Snap-In Plug, Equipment Is Adapted To Sound In Water/Acrylic, 1 Mhz.