A 6X4 part of a tube is a tube that has a circumference of 6 inches and a length of 4 inches. It is commonly used for DIY projects, such as for constructing furniture or for plumbing works. This type of tube is usually made from metals such as aluminum or steel and can be used for various applications. It is typically available in various lengths and thicknesses. Its most common applications are in air conditioning systems, water heaters, boilers, fuel tanks, and heat exchangers.