The surface of this kind of tube is smooth and the tube is colorless. The properties of the tube are: high purity(SiO2>99.99%), abrasion resistance(any acid except HF acid ). fire resistance(softening point 1700 centigrade). low coefficient of thermal expansion(5.5x10-7/centigrade, heat the tube to around 1100 centigrade, then put it into ordinary temperature water, the tube won't crack, ); The surface can be done with gold plating. Gently using sizes: single outer diameter X double outer diameter 8x17mm, 11x23mm, 15x33mm length 400-4000mm lianyungang inpuquartz factory