This is pretty basic but I have not seen people talk about voltage and amps for these fans to work. 1: Most all computer fans are brushless ball bearing type running off of 12V DC (you want brushless!!!!) 2: They can only be hooked up one way (likely diode controlled) 3: Amperage of the wall plug in (transformer) does play a roll. 4: Voltage does not have to be spot on! Taking those things into consideration, your likely looking for a 12V 500mA (1/2 amp) transformer. Most fans will state the proper operating voltage and amperage. You should be ok going above this a little. So if your fan is 12V .30amps then you are looking for a 12V 300mA transformer to meet the exact specs. In reality you can go with a 7V, 10V or even 15V BUT you have to gauge how fast the fan is going. Running off of a 7V or 10V transformer will likely slow the fan to much, depending on the side of the incubator. OR in turn a 15V might be to fast for the incubator. Anyway, what I'm trying to say is you have some wiggle room here, don't be freaked out if you can't find a transformer that hits spot on. Ive hooked up a 30V transformer to a 12V fan and it work's, although a little fast for what I need. The best I can really think of is a 120MM fan, which in my opinion pushes a good amount of air around while keeping the noise down... If you have any questions on this feel free to ask as I know some of you might not understand exactly what to do with your dump find computer fan!