Scepter - Under Seat Portable Marine Fuel Tank - 6 Gallon - 10511. The "ECO Check" line features a EPA/CARB approved fuel cap and a Low permeation tank that virtually eliminates fuel evaporation. With a convenient combination fuel pick / sight gauge, this 6 gallon portable marine fuel tank fits comfortably under the seat of your craft and features molded feet for increased stability.. Features:. Size - 6 Gallons. Gauge - Yes. Dimensions - 19.3"L x 12.2"W x 10.2"H. Easy to Transport. Compact Design for Convenient Under-Seat Storage. Made of UV Stabilized, Rust and Corrosion Resistant HDPE for Maximum Durability. 2-Way Vented Cap. Designed to meet international standards