DURAN^® burettes are made of highly chemical resistant borosilicate glass 3.3 and are only used for titration. The quantity of liquid required for titration, which is unknown beforehand, can be precisely read off once the reaction is complete.Class AS, with Schellbach stripe. With lateral standard taper joint stopcock with PTFE key and PTFE intermediate stopcock, blue inscription, incl. bottle and rubber bulb. With certificate of conformity and batch certificate.