The construction of the 381 is very durable and features Glass-Filled, Nylon-Tough front and rear housings for UV and chemical resistance.  The mounting strap, rivets and grounding strip are gold plated / *pure silver plated, and solid brass.  Marked with Blue Star audio Grade.

381 AU = gold plated

381 AG = pure silver plated

381 RH = Pure Rhodium plated