So I went and bought some fans for my stealth grow box. See my grow journal link on my signature below. I bought two 80mm fans which fit snugly over my 4" holes. There is one at the top for exhaust (hot air at the top), and there is another one at the bottom for intake. It is conveniently located beside my A/C duct. The fans are rated at 12V, 500mA, and shuffle about 35 cfm. This is a complete exchange in my 2x2x4.5 box about every 30 seconds. Ideal. I bought an unregulated 12V power supply for them and rigged them in parallel. The power supply can handle 1A, so this also is perfect. I suppose if I wanted to get anal about it, I could build a regulating circuit for another few bucks, but at 16V, I'm pretty sure the reduced lifetime of my fans will not occur during this grow. I may even upgrade in a couple months to 100mm (4") fans. I plugged it into my timer circuit, so the intake and exhaust fans will only go during the daylight hours. I wonder if this is an ok idea, or if they should be ventilating 24/7. I also bought a $5.00 desk fan to keep the air circulating inside the grow box. Enjoy the pics... comments welcome!