I guess I'm the cautionary one here... I suspect you're talking walmart or harbor freight jacks. They are not reliable, I've had several of those jacks and they have: split in half, leaked all the fluid out (x4), and (the most fun one) rather than stopping at its limit, popped out the top (more specifically, fell over and out of the base). Even putting those issues aside, bottle jacks are unstable on anything but flat, solid ground... hi-lift jacks are cheap (less than $50), and the knock off ones are nearly as cheap as the cheap bottle jacks. Of course, they're unstable too and can take your teeth out if you do it wrong - but it's so much more of a jack, so much more useful, and honestly - cheap is great for anvils - not so much for things that will put your life at risk if they unexpectedly fail.