These double flare plugs are made from ceramic with volcanic glow glass glaze. They have a wearable area of 5/16" between flares. Each plug is hollow to reduce the overall weight and act as a diffuser for essential oils (optional). Just 1-3 drops per hole will last about 1-3 weeks. These are hand made, so please allow slight variations in the glaze colors and size tolerance of +/-0.5mm. Choose your size below.