Specifications: Structural Half Round Vault Skylight shall be as manufactured by Plasteco, Inc.(800-231-6117; Fax 713-453-8372). All extruded aluminum shall be 6063-T5. Exterior exposed aluminum can be mill finish, (clear anodized, bronze anodized, or baked enamel (color)). Model 312 outer acrylic can be clear, (2412 bronze, or 2447 white translucent). Model 313 inner acrylic can be clear, (or 2447 white translucent). Rafters shall be mounted on nominal 4 ft. centers. The skylight shall be designed to support 20 psf live load and a 20 psf wind load. Curbs (by others) shall have a minimum thickness of 5-1/2Ó and shall be designed to support the skylight and thrust of a 20 psf live load.