DIN 168-1 thread, USP<660> (Spectral Transmission) and EP (3.2.1), graduated Manufactured from ambered DURAN® borosilicate glass 3.3. DURAN® is a neutral glass, classified as a Glass Type I according to USP <660>, EP (3.2.1) and JP <7.01>, and meets ASTM E438, Type I,...7.01>660>660>