This blue handheld vacuum pump features a built-in gauge reading in inches of mercury (Hg) and a 19.5-inch rubber tube with 6mm inner diameter. The pump displaces 725mL of air at a rate of 15mL per pump and can reach up to 29mmHg. The pump is suitable for air pressure experiments, vacuum filtering, and leak checking. Not intended for heavy continuous pumping. The rubber O-ring may roll in the cylinder at approximately 20 Hg after about 10 pumps and can be serviced by disassembling and oiling. Not for automotive use.