Material: BK7 grade A, fused silica or other optical glass Dimension tolerance: +0.0/-0.2mm Clear aperture:>80% Deviation: 180 deg +/-3arcsec +/-15arcsec Flatness: Lambda/4 on big surface, Lambda/10 on other surfaces Surface quality: 60-40,40/20 scratch and dig Wavefront distortion: Lambda/2 at 633nm Bevel: 0.2mm to 0.5mm Coating on input and output sides: uncoated or AR coated upon requests