The water bottle fuel tank has become very popular due to the extreme light weight and increased visibility for the plumbing in the tank. This tank started out as a 591ml Smart water bottle. That works out to roughly 20 ounces. It comes ready to install just as the picture shows with tygon tubing for gasoline powered airplanes. The polypropylene fuel inlets are designed for 1/8 inch (3.2mm) fuel line, and they are mounted and sealed. This is the perfect size for today's 60cc engines.