These tamper-resistant barrel nuts are constructed of steel and come in a chrome plated finish. The heads of each barrel nut are constructed with a one-way security feature which allows for easy install with a flat screwdriver, but require the use of a one-way fastener remover tool. See Sentry Supply part 650-7901 for screw sizes 6-8, Sentry Supply part 650-7902 for sizes 8-10, and Sentry Supply part 650-7903 for sizes 12-14, or Sentry Supply part 650-7904 which includes one of each one-way screw remover hand tools.