First surface mirrors are aluminized on the surface nearest the incident light. Light is reflected off the mirrored surface and does not pass through any glass, minimizing light loss. Reflection rates are around 85 - 88%. Enhanced Aluminum mirrors have an average of 95% reflection.
51mm and Larger Experimental Grade First Surface Mirrors are offered in several experimental grade options. Grade 1 is standard optical glass, edged, free of visible scratches, chips, stains, or oxidation. Grade 2 is unedged, non-optical glass, small chips, slight stains, or other defects.
Note: Specifications for experimental grade optics may vary as much as 10% from those listed. Also, no additional information is available other than what is provided.