These brass drain plugs are for use when mounting Moeller drain tubes inside your boat's transom. Fully adjustable and waterproof design includes a neoprene seal and will not leak or jar loose under vibration. Corrosion-resistant construction is great for marine applications. Simple two-step installation. 50 plugs per container. Fully adjustable & waterproof design Corrosion-resistant construction | Moeller 1" Brass Turn-Tite Plug, 50-Pack