Yes it is the breather hose. its the only one that is 3/16 inch. it just goes to the bottom of the bike. yeah use 3/16 barb fittings. You don't even need clamps. You can use a venting gas cap. But I did a breather tube on my special order tank incase i ever wanted to fuck around with it in the future. oh and mine is 6 by 13. I remembered wrong when i posted all this before. Also make sure u order it with the cap off set to the side. and i ordered the 1/4 npt bung over the 1/8 option. fuel filter is not needed.