Manufacturer's part #06 LGD 316. Original price: $131. This is 1.8mm diameter by 7.52mm ling with a design index of 1.636 and a numerical aperture of .60. Acceptance angle is 72 degrees and fractional pitch is .50. These are well suited to coupling the output of a diode laser into an optical fiber. Easily achievable aberration correction without complex multielement systems or aspherics. Reflection is reduced to less than 1.5% per surface with the Broadband AR coating. Gradient index lenses (GRIN) are made from Selfoc, a radial gradient-index material. These can transfer collimated light from one end of the lens to the other. Also, can transfer an inverted real image from one end to the other. Unused. This is actually so small it comes in a pill capsule!