Outlet Connections: 9/16"-18 LH. Oxygen uses a 9/16"-18 RH outlet connection, while acetylene uses a 9/16"-18 LH outlet connection. Fitting Type: B-B Fitting. Premium Brass Build: This oxygen acetylene regulators main body are built with durable brass for excellent airtight sealing, strong high-pressure resistance, and long-lasting durability in demanding working conditions.