This tank hasn't worked since it arrived. 2 probs...the inner o ring on the bottom cap is too tight and it won't slide on the cart once its put together. And...the outer o ring on the same cap doesn't hold the tank well....slides right off with very little provocation. No matter the hole size I put in the cart...it leaked all over. I'm going to shop around for some tubing at Lowes or someplace....find a cheap replacement to go with the caps. .6"......got it....thanks!