Simply Auto AC01 12V Air Compressor and Tyre InflatorUnderinflated tyres wear faster, use more fuel and handle worse, and most cars run at least one soft tyre for months without the driver noticing. Simply Auto 12V Air Compressor plugs into the car's 12V socket and sorts it on the driveway, without queuing at a garage forecourt or feeding a machine that may or may not be accurate.The gauge is analogue and reads in PSI, BAR and KPA. Whichever unit is printed on the placard inside your door frame, you can work in it directly rather than converting.The power lead runs to 2.5 metres and the braided hose adds another 40cm, which between them cover all four wheels of most cars without starting the engine and moving it round.From completely flat, the compressor takes 9 to 10 minutes to bring a 175R13 tyre up to 30 PSI. In practice most jobs are far quicker than that, since topping a tyre up from 26 to 32 PSI is a fraction of the work of filling one from nothing. Maximum capability is 300 PSI, which leaves plenty of headroom above the 30 to 35 PSI a car tyre actually runs at.Three screw-in adapters come in the box, so the same unit handles bike tyres, footballs, airbeds and inflatable toys.At 120mm by 135mm by 72mm and 420g, it stores in a boot or a cupboard without claiming much space. Always inflate to the pressure specified for your vehicle, which is on the placard inside the driver's door frame or in the handbook, and never above it.