RG® High Quaity Lens and Mirror Set| Set of Concave, Convex Mirror and Concave, Convex Lenses. 50mm diameter,Focal Length-20 cm : Amazon.in: Industrial & Scientific
EISCO High Quality Glass Lenses, Set of Four, Double Convex & Concave Lenses of Dia. 50 mm, Polished, High Quality : Amazon.in: Industrial & Scientific