Comes with O-ring, leak-proof. Made of brass material, strong and durable, corrosion-resistant, and rust-proof. The depth of the hole is 7.2mm. Effectively prevent slippage and wrench damage. Product description Name: First stage Scuba Diving Port Plug Material: brass Color: Silver Low pressure plug: Diameter: 12mm/0.47 inch; Height: 9mm/0.35 inch; Screw Thread: 8mm/0.3 inch High pressure plug: Diameter: 13.5mm/0.5 inch; Height: 9mm/0.35 inch; Screw Thread: 10mm/0.4 inch Package Contents: 1 piece high pressure plug 1 piece low pressure plug Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.