Clear vial, 33 Expansion borosilicate glass USP Type I, Class A. Amber vial, 51 Expansion borosilicate glass USP Type I, Class B. Graduated write-on marking spot area, measures 0.5, 1.0 and 1.5ml. Strictly quality control to ensure the consistent size of each lot of items. The ever flat-bottomed guarantee consistent matching between vials and truly neck 8mm for Standard Glass insert.