These are professional optical lens with 45mm focus length, It’s very good for you to DIY your own Virutal Reality Device like Rift, Google cardboard etc.
Diameter 37mm Convex Acrylic Lens
This 37mm diameter lens can give you much better virtual reality experience than the small lens.
Size: Diameter: 37mm, Focal Length: 45mm
Visible Light Transmission: 93%
Net weight: 12g
1x Diameter 37mm Convex Lens for Google Cardboard Virtual Reality VR