A metallic cylindrical tubular needle cannula (1) is subjected to a metal etching liquid inside the lumen (7) thereby increasing the inside diameter and enhancing the flow properties while maintaining the outside appearance. The inside wall (5) is further provided with a collapse zone (10) manufactured by radiating heat (11) to a specific outside area of the needle cannula (1 ) thereby increasing the aggression of the etchant. Further two different methods of in- process testing of the inside diameter of the needle cannulae using any fluid gas are disclosed.
