Dehydrator plugs are used to prevent rust and corrosion in engines while in storage. Contain silica gel which turns from blue to pink when moisture is absorbed. Reusable gel may be reactivated (after removing from reservoir) by heating gel crystals on cookie sheet for approx. 16 hours or less at 250 degree F. Once crystals turn blue the crystals can be replaced into plastic containers. The 14 mm plugs are non-reusable.