Will either of these work? I was concerned the ones on the left were too big and the ones on the right were not the right kind? I will be using a 2000mL flask and 1 3/8" bar
i wouldnt use the ones on the right for sure, the left ones would certainly be strong enough, but they are too big imo. I think they might keep your fan from turning. I know some have gotten the smaller rare earth ones at radio shack and ace. got mine at harbor freight.
I can say for sure the ones on the right will not work. They will not be strong enough. The ones on the left, well I cant tell. I know you need a rare earth magnet. I think they are different from the one on the left though. I'd do some research first. When I built mine I purchased 2 rare earth magnets of a website for next to nothing. I think shipping them was more $.
These were the only two that Ace had, I'll have to check out radio shack or try to find a local harbor freight...or locate the proper size on ebay perhaps these that are about 5/16th?
I used 2 of the magnets on the left, they are plenty strong enough. I used them on a 120MM computer fan, I can stir over 3 gallons using a 1-1/2" Length, 5/16" diameter stir bar.