Each lid has a 4.1cm (about 1 5/8″) hole in the middle, which fits a variety of pendant, vanity, and other light fixtures that use a 1 5/8″ fitter opening. Your fixture should have a plastic locking ring that screws on and holds the glass shade in place – that ring will now hold your jar with this lid in place. There are other standard “fitter” sizes, so be sure to measure your fixture. Our Lowe’s has a large selection of vanity lights and sconces that are sold separately from the glass shades (including the one in our pictures). The lids are ventilated for heat dispersion and air flow. Use them with a normal jar and a low wattage LED bulb, or use one of our open bottom jars with any type of bulb. Made from stainless steel or tin-plated steel, depending on the style. Stainless steel will not rust, so it is most appropriate for use in bathrooms and humid locations. The other styles are made from steel that has a rust resistant coating, but it may eventually rust in very humid places.