Pure copper battery core:Small resistance, energy saving,high strength, stable output and lonr service life Imported steel:Precision machining by 7 types of lathes with high precision, stability and durability Processing technique:The zinc alloy die-casting surface has been sandblasted twice and is carefully crafted Double pump head:Double pumping, double air outlet, fast pumping speed, can be connected in series or parallel, good material, one machine can support two machines