Optical domes are lenses with two concentric spherical surfaces. Sometimes they are being referred to as bent plan parallel plates. Consequently it is customary to define parallelism between two surfaces as the maximum thickness variation between the two surfaces. In perfect domes the convex radius is equal to the sum of the dome thickness and concave radius,respectively uncoated or with an antireflection coating.Slight departures from that rule are sometimes desired. These protection covers are high quality optical products which are produced through precision polishing. They ensure clear, distortion free protection for your underwater camera objective or other sensitive equipment.Yutai Optics provides domes from glass, quartz, depending on the temperature, shock and scratch resistance required. These items will be manufactured on customer request only.We recommend thickness at least 4mm for customer as production cost will be better than the thinner ones.