Pneuflex's SPM 04 is stainless steel 316 bulkhead union straight push in fitting with equal 4mm hose push-in connectors at both ends, designed to connect two pneumatic tubes with same diameter 4mm through a panel or other barrier and fixed by two bulkheads. 4mm bulkhead union pneumatic fittings utilize stainless steel 316 as a tough steel sheel to withstand the corrosion environment.