R6 polyiso insulation in curb and cover help to reduce energy costs. Curb and cover are constructed of 11 gauge weather-resistant, mill finish aluminum, 18 gauge cover liner and continuous EPDM gasket. Counterbalanced springs and locking hold-open arm allow single-handed operation of cover so that operator can maintain 3 points of contact with ladder. The indented Diamond Grip™ design secures the roofing membrane and backer rod for easier installation. Hardware is zinc-plated including inside and outside handles and padlock hasps. Tested to 50 psf wind uplift