This is a gasket kit consisting of a conductive gasket, stainless steel screws, nuts, and washers to connect two waveguide flanges together. The FMWGK1021 is the kit made expressly for WR-90 CPR-90G waveguide flange. The gasket is made of Shore “A” 85 silver-plated copper impregnated silicone elastomer. The screws, nuts and washers are made of stainless steel. Fairview has waveguide gaskets (both conductive and non-conductive), screws and other accessories that you need for your waveguides. Often people can forget to order items like screws or waveguide supports. Fairview has a full line of waveguide accessories available for same day shipment so that you do not have to wait for weeks to get your system working.