Never had much luck with aluminium jacks, they just seem too flimsy for heavy duty use.
Whatever you get, make sure you can get a service kit for it.
I've had a 3 ton Sealey Yankee for longer than I care to remember, I fitted a new seal kit about 6 years ago when it started to leak. Seal kit was 6 quid and tge job took about 30 mins!
Arwyn
