These brushes are specificaly designed for cleaning test tubes. Radial Tip brushes have formed brush sprays at the tip allowing thorough cleaning of all sides. Stainless steel wire stem Radial Tip brushes are extremely durable and provide superior performance. Tied Tip brushes are designed to enter small openings of bottles and tubes, then expand to clean the sides and bottom without scratching . Sponge Tip are made to expand to give a more thorough cleaning while also protecting from scratches. The adjustable test tube brush spreads apart to fit all sizes of test tubes.