Universal Power Conversion's miniature fittings include Barbs, Plugs, Nipples and Tees. Offered in Brass, Nickel Plated Brass, Stainless Steel and in a verity of plastics. Nylon Material: Black is the standard color for all nylon fittings. White, Blue, and Red Nylon are available in the plugs, nipples, and barb fittings. Polypropylene Material: gray is the standard color for all polypropylene fittings. These miniature fittings are used for countless applications.