Good for up to a 4 x 4 grow tent... This little guide will show you how to make a natural co2 bag for your grow room and unlike others that you have to pay big buck for this will cost you only a few dollars and give you great results because it works inline with the environment of your grow room. What that means... the co2 that is released is based on your grow rooms environment which will pretty much release all the co2 that your plants can take in based on the current temperature, current RH, and current barometric pressure. During the first week this bag will release anywhere from 400ppm(s) to 600ppm(s) of co2, but once the mushrooms beginning eating away at the medium you supplied them the released ppm(s) will jump up to 840ppm(s) to 1090ppm(s). That will happen in about 4 to 5 days after the bag is made. The bags last a good 4 weeks, then the ppm(s) will drop. The things you will need... a 1 or 2 cup measuring cup 1 small corrugated cardboard box. 1 8oz package of the cheapest sliced mushrooms you can buy. 2 tbsp of granulated sugar. old coffee grinds from the last pot of coffee you made. 2 cups of distilled water. 2 twist n' tie 1 gallon, 1.5 gallon freezer bags. 1 old powerade bottle. 1 5ft of rope, 3/32 or whatever you have on hand. 1. cut your cardboard into medium sized pieces... you will need (2) cups per bag. 2. place the cardboard in a bowl and pour in (2) cups of distilled water. Let it soak for 10 minutes, pour 3/4 cup of water out of the bowl. 3. add 2 tbsp(s) of sugar to the bowl. 4. add your old coffee grands to the bowl without the filter. 5. the mushrooms we are adding to the bowl. 6. when adding the mushrooms break them up in pieces and mix everything up good. 7. take your powerade bottle and cut the very top off of it. 8. place the mix in a DOUBLED UP bag, use (2) bags, then on top place the clear powerade top on top. Then tie the bag closed. 9. drill about 10 -15 little holes into the black powerade cap. 10. Twist black cap on to the clear bottle top, and then use a punch in each hole to penetrate the plastic bags. 11. the completed co2 bag 12. Place bag into a dark cool area for 48hrs before hanging it into your grow tent. Here is a picture of one of these bags hanging in a 3 x 3 tent. Here is another picture. The tent is a 3 x 3, it has just (1) 39 day old from seed Auto Bubble Gum, that has pretty much filled up the whole 3 x 3 tent. Have fun... F!