A twisted in wire brush is known by many names, such as spiral, tube, flue, bottle, pipe, boiler or power brushes. They all represent the same brush construction. In essence, a piece of wire is doubled over and fill material is inserted between the fold of the wire stem. Often, the fill material is made of stainless steel or aluminum. The wire stem is then twisted into a brush. Ends of the brush can vary, depending on your needs. For example, a twisted-in-wire brush can have a cut tip, rounded tip or filld tip. It can have a long end or handle, a short end, one with a ring, loop or cut.
Typically the fill material is located at one end of the brush, and the handle extends from it. However, the fill can be centered in the wire, with two long ends, one on each side.