This specification covers general requirements for laboratory glass volumetric apparatus of Class A and B. The volumetric apparatus shall be manufactured from glass of suitable chemical and thermal properties, and shall be as free as possible from visible defects. Glasswares with a flat base shall stand firmly without rocking when placed on a level surface. For those requiring stoppers and stopcocks, glass stoppers shall be interchangeable while plastic stoppers used as alternative to glass ones shall be of inert plastic material. Stopcocks, on the other hand, shall permit smooth and precise control of outflow. Glasswares shall have clean, permanent graduation lines of uniform thickness confined to the cylindrical portions of their cross section, with the graduations lines being of Pattern I, II, or III and the unit of volume being cubic centimetre. Units of cubic decimeter or cubic millimetre may be used in special cases; however, only one unit of volume shall be used on the same piece of apparatus. Aside from graduation lines, the glassware shall bear inscriptions of the capacity, the temperature at which it is to be used, the method of use (whether to contain or to deliver), and for those that deliver though an outflow nozzle, the time required to empty the total nominal capacity with unrestricted outflow. Per service requirement, additional provisions may be specified as well.