In order to ensure consistent argon flow in the stopper gas channel and improve argon bubble performance in the slab casting mould, two patented new technologies CSC (Clean Stream Cartridge) and SHP (Slot Hole Plug) were applied in the argon purging stopper designs. The novel stopper designs can maintain a stable back pressure and argon flow in the argon line during long sequence casting, eliminate pressure increasing at the start of the casting, even distribute gas bubbles in the mould leading to improved mould flux melting and lubrication, reduce mould level fluctuation and so on.