Individual Air Tanks for On-Board Air Systems. Steel tanks with black e-coating for corrosion protection. 8 to 10 bungs depending on tank size provides many attachment options. All tanks have 2 x 3/8in NPT bungs. 4 x 1/4in NPT bungs located around center circumference for mounting tank with feet in 4 different mounting positions and have a drain cock positioned at the bottom.