Highest Impact Resistance of All Transparent Shield Materials Laboratory workers are protected by a 4.7mm (3⁄16") thick clear polycarbonate barrier. Stable three-sided construction provides front and side protection against flying debris. The heavy steel perimeter base is coated with blue epoxy. Plated steel bolts, nuts and washers are used for assembly. Outside base width is 50cm (191⁄2˝) and17cm (61⁄2˝) front to back