Easy-to-fit Heat Shrink Tubing or roll-on 'O' Rings squeeze Engine Turning Brush bristles together so they don't spread out. Keeps those crisp, sharp, deep 'swirls' that set a professional jeweling job apart from the rest. Adds a new dimension to your jeweling capabilities; increases brush life too! For the absolute best results, do all your jeweling with the Brownells E/T Brush Holder. Heat Shrink Tubing goes on easily; just cut into ¼' sections, slip over end of brush and heat with a match, hair dryer or heat gun. SPECS: Set includes: (6), 3/16" (4.8mm) diameter brushes; (12), 1/4" (6.3mm) diameter 'O' rings; and (1), 4" (10cm) length of heat shrink tubing (enough for 16 pieces).