This is a DIY oil tank kit, which includes all the parts you need to fabricate your own custom oil tank for your custom motorcycle. Customers have also used these tanks for many other uses other than just motorcycle oil tanks. They can be used for catch tanks or fluid reservoirs for all sorts of applications to suit your needs. This is a weld together kit for those who dont mind doing a little welding and grinding themselves and saving some money in the process. This also allows you to place the fittings and filler bungs in the exact locations to fit your custom project as well as the option to trim down the tubing length or overall length of your tank. This is the only way to guarantee the best fit. The tank holds 3 1/4 quarts with room for air, for oil expansion as the oil warms . We also offer a 6" diameter kit and also oil tank kits with flat end-caps.