TECHSPEC® Precision Dual Surface Optical Flats are precision ground and polished to the stated accuracies on both surfaces so that either face may be used for test applications. Both surfaces are tested and certified by our Zygo Interferometer. Each flat ships in a durable storage case for permanent protection. TECHSPEC® Precision Dual Surface Optical Flats λ/20 flats that are 76.2mm or larger also include a certificate of calibration. These dual surface flats are uncoated and offered in diameters ranging from 25.40 to 203.20mm.