We supply optical windows,mirror,flat,glass. china star optics offers all types of windows made from different materials. Special size and materials are also available upon request. In addition, we provide a variety of single layer or multiplayer anti-reflecting coating on optical windows. Please refer to coating chapter for more information. specification of our optical windows as follow:*material: bk7 or other materials*length tolerance:+/-0. 01*width tolerance:+/-0. 01*center thickness tolerance:0. 005mm*surface quality:80-50 to 10-5 scratch/dig*surface flatness:*parallelism*clear apenture:80% -- 100%