What is an 18 gauge needle used for?

Hamilton 18 gauge laboratory needles are commonly used for gas and liquid sampling.  These needles are made of 304 stainless steel with an outer diameter of 1.27 mm and an inner diameter of 0.838 mm. They commonly feature various point styles and Metal (N) or Kel-f hubs which are compatible with Luer Lock syringe terminations.