8mm Screw Vial Larger opening than standard narrow opening vials by 40%, preventing syringe problems. The special thread design ensures a consistent seal. 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.