DIC Fasteners supplying https://www.dicfasteners.com/cap-nuts.php">Cap Nuts, Stainless Steel Cap Nuts, Flat Cap Nuts in brass, plastic, steel with a nickel plate, 18-8 stainless steel. Cap Nuts help maintain better insulation for different uses, like buildings, airplanes cars, and boats. We can provide acorn nuts with a washer base for both open and closed acorn Cap Nuts.