We offer a wide range of material types and sizes of brushes and stars that are used with the vipers. (Stars are a single layer flat brush.) The fittings supplied with vipers allows the use both types. Perlon is a default material used for cleaning flues and lined chimneys. This is a plastic material that will not damage any lining system. These brushes and stars are available in a combination of soft, medium and hard varieties. PEK brushes are largely used on lighter applications such as cleaning oil, gas, biomass flues and often used to maintain Aga/Rayburn cookers. There are two types of stainless steel varieties of stars/brushes. They are considered a harder material and harsher than other types.