For sampling gases, smokestack exhaust systems, air quality, or calibration of instruments in the field. Flexible, sturdy bags are made of 5 mil thick FEP fluoropolymer film. Leakproof. Inert to most chemicals. Available with either a nickel-plated brass on/off valve which accepts 1/4"" I.D. flexible tubing or PTFE/silicone septum in polypropylene housing for use with a hypodermic needle. Individually packaged.