GSC International 4-90911. Lens Double-Concave Glass Lens, 50mm Diameter, 20cm Focal Length.
The glass lens provides superior optical clarity, lower distortion, and minimal chromatic aberration (color fringing).
The lenses are well-made to avoid spherical aberration, where light rays from different parts of the lens don't converge at the same point, resulting in blurry images.
This is an affordable, good-quality lenses which performs well for many types of classroom experiments.
PRODUCT WARNINGS
WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
Our products are not toys. Use in a laboratory or educational setting only. Not for children 13 and under.