Typically, using your hand pump while out on the trail or on the side of the road to pump up the flat tire you just repaired means simply guessing how much pressure you've added, because hand pumps rarely have pressure gauges. Lezyne has stepped in with a predictably intelligent solution in the form of the ABS Pen Gauge. The in-line gauge is at the pump end of a flexible hose, similar to the hoses you find on other Lezyne pumps. It can be used as a replacement to the stock ABS Flex Hose found on Medium and Large hand pumps, but it's too large to fit in size Small models. The gauge cannot be used independently of an applicable Lezyne pump. The valve end of the Lezyne Pen Gauge hose has Lezyne's Flip-Thread chuck, meaning it screws on to both Presta and Schrader valves. Maximum pressure reading is 120PSI.