Fuzhou siaon optoelectronic technology co., ltd. Provide bk7 window bk7 window is the most common type of window, it has good performance over visible and near infrared wavelength region.the refractive index is 1.5168 at 587.6nm.Material: bk7 grade a optical glassdimension tolerance:+0.0-0.2mmthickness tolerance:+0.0-0.2mmclear aperture: >85%flatness:2@632.8nmsurface quality:60-40parallelism:1 arc minbevel:0.2mm to 0.5mm x 45coating :uncoated