I have a 60 gal RDS gravity fed tank. It is DOT certified in all 50 states. They have roll over shut off. As far as diesel is concerned these tanks which feed directly to the main tank are legal even in Calif. It is illegal to feed directly to a carb or injectors. I researched a number of tanks out there before I bought RDS and all of those are DOT certified. I bought mine from Union Hydro on sale for around $700 with the install kit. I spent about $20 more for stainless bolts, nuts etc. Installed myself without issue. Last big trip was over 5,000 miles and I decided where and when to get fuel. I travel with my wife and three little dogs. Now I stop for breaks whenever they need them not timed to fuel stops. Heck I only get fuel about every third day anyway.