When the inlet pressure and outlet flow change, to maintain a stable outlet pressure. Hyperbaric oxygen in the bottle, dissolved acetylene gas after decompression, uses a pressure reducing device. Double tube, provide welders, reduce costs. Features: Mainly used for welding, cuallied processes, etc. Product Description Material: Metal Color: Gold Package Contents: 1 x CO2 Mig Tig Flow Meter Only the above package content, other products are not included. Note: Light shooting 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 +/- 1-3 cm.