My bike is the one Jonny mentioned with the plastic tank, and you can see pictures of it there. Its 2 gallons. The only difference is the size of the fuel line. The stock fuel line is 3/16, I am running a 1/4 line. That may not apply on every tank, it depends what size nipple the petcock has. Basically, if you are willing to get a little creative with the mounting technique, you can probably fit just about any tank you want on your bike. I have seen all kinds of tanks on bicycles, from in-frame designs to Harley Sportster tanks, and everything in between.