| GENERAL CHARACTERISTICS ITEM DESCRIPTION | MATL. OPTICAL GRADE PYREX GLASS MEETING REQ. OF MIL-G-174 AS APPL.; SIZE 5.0 IN. DIA.,0.5 IN. THK.; GENERAL SPEC. MIL-O-13830A AS APPL.; REFLECTIVE SURFACE- FRONT ALUMINIZED PER MIL-M-13508; PROTECTIVE COATING- SILICON MONOXIDE PER MIL-M-13508; REFLECTANCE- NOT LESS THAN 85 PERCENT; FLATNESS- WITHIN 1 FRINGE; PARALLELITY- WITHIN 3 ARC SEC. SURFACE TO SURFACE |