Test it before buying. You might need a friend to stand on the demo jack while you test it. No doubt you'll be able to pump it up and lower it, but you need more than that. Just how the release works is important.
I've been using quality jacks for years. You get used to their operation. Then I went out and bought one for home use. I failed to realise that cheaper jacks have poor release valves that are not nearly as good as the ones I had been used to. Not only was the release difficult to operate, but it also tended to be either open or shut.
A quality jack will allow you to open the release valve slowly. So, that the jack lowers slowly. The last thing you want is for the car to drop to the ground suddenly. Or drop onto a safety stand with a crash. You may be using the jack to support the gearbox or engine. You may need to lower it a fraction of an inch, only. The last thing you want is to find you've suddenly dropped it to the ground.
