This 10x 21mm triplet loupe from Hobby Tool Supply uses 3 lenses to provide a sharp image with little to no spherical aberration/distortion. Unlike chrome loupes, the matte black finish helps reduce chromatic aberration. Coupled with the reduction in spherical aberration from the three lenses, this loupe provides a very accurate, sharp image when used correctly. The metal cover has a miniature split ring which allows you to attach a chain or string for extra security while you use your loupe in the field.