I love these things..l have a tyre inflator in the garage and it is really useful (12v cig lighter plug) It is easy to use & the pressure gauge is not far off accurate..Recently aquired a similar much smaller item from Aldi..£3.99 & small enough to fit in a tankbag pocket BUT : the pressure gauge is woefully inaccurate-this is Dangerous to the uninitiated. Gauge reads 45psi when the actual is 15psi less.
It maybe the item l have is not typical, but beware if you use one. The thing l like is if you get a puncture it will in most cases be a slow puncture, so this item will provide a 'get you home' solution.
Not ideal but with a common sense application, ie careful, it can be a life saver; Dark rainy night, flat mobile, ten miles from home, isolated location, sub zero etc, etc.. A few options, 1, abandon the bike(it will get stolen) & walk home..2 hours ?
2, Push the bike home (4 hours+hernia)
3, Reinflate with said article and ride home cautiously..
£3.99 is a seriously cheap solution to a sh**t situation..

That's the problem with cheap Chinese stuff it sort of does the job. I carry a puncture kit with co2 bottles with me. Never needed it yet but I will at some point                                                                                                                                                                             

You've got the export version for use on the moon or Mars. That's why it's out by 15psi or 1atm.