I've been in the market for a tank for a few months now, and I've used Ebay as my main place to locate a tank. Problem is, sellers don't have all the information neccessary to sell their product. You need to know a couple of things about you gun before finding the right tank. Like what air pressure is prefered for your model gun, whether it has a chamber for CO2 or is made more for HPA. Sellers need to list more info about the tank to help us the consumer know what were purchasing. For instance, almost none of the tanks up for auction right now tell what the output pressure is on the tank. Is it a HP or LP? A high pressure tank usually has an output of 850 psi, where a low pressure tank has a output of 450psi. These are very important to the buyer, yet many don't cover it. Also, what is the Hydro date? All tanks have to be re-hydroed every 4 or 5 years, and it can be a pain to get done, so buyers would like to know how long it will be before the tank they are purchasing is going to cost them even more money. I hope someone finds this helpful, and I wish more sellers read the reviews before putting things up, so they would know what their customers need.