I have 2 jumper packs,
this little Red Fuel thing-
redfuel.jpg
and this Stanley thing-
stanleyjumper.jpg
I don't get to use them much, but when I HAVE used them, they never failed to start my cars or truck.
The little Red Fuel unit amazes me. No, it won't start a skid-steer or the 8.3 Cummins in our motorhome, gonna need a lot more grunt for those things. But for daily drivers, fantastic