Bristle Brush – 25 x 75mm, 20cm. Bristle Size 25 x 75mm, x20cm lgth. Our various test tube brushes feature good quality bristles mounted on heavy gauge, twisted galvanized wire. They have a double radial tufted end which makes it extremely easy to clean the entire burette or test tube, including the hard to reach bottom of the tube. They come in four all-purpose sizes. Image may vary.