The Model GV-100-S-TR Gas Sampling Pump can precisely collect a sample volume for a detector tube. The full-stroke (100 mL) and the half stroke (50 mL) positions are marked exactly by the red line on the pump shaft, and the handle is precisely locked at those positions. If you pump fully "n" times by allowing for sampling time intervals, a volume of 100 mL x "n" can be sampled. Each detector tube is calibrated based upon a prescribed (standard) volume of sample. Also, the pump piston has been designed with a smaller diameter so that the handle can be pulled out with even less effort. Gastec piston sampling pump design proves you with advanced non sparking design and superior features. It is a convenient handy size easily carried, it weighs a mere 230 g. The built-in tip breaker incorporates a diamond edge that cuts the surface of the detector tube. This makes the tip breaking much easier, safer and convenient. The pump piston has been designed with a smaller diameter so that the handle can be pulled out with even less effort. The pump body is covered with a soft elastomer. The pump is make of non-sparking materials of ABS resin. The attached flow finish indicator tells you automatically when the stroke is complete. When the white disk pops out, the sample is complete.