you guys are really making bit of a mountain out of this mole hill. I would have thought some decent kitchen scales would be accessible by most reefers, but if not - go for 1500ml - it's really not going to create that much of difference. Besides it's consistency we are all chasing over actual figures. Makes no difference to me if it says 7.4 or 7.6, as long as it has a benchmark to try and stay at.