I find it hard to believe that something like this can generate much vacuum and its specs aren't listed. My guess is that this isn't much better than sucking the air out of a ziplock bag.
If you've got $20 to blow, it might be worth a shot. Usually when I see those 2 for $19.95 offers, I usually assume I might as well light a cigar with a $20 bill. At least the $20 would have generated some heat.