These Pyrex® flat-bottom boiling flasks have full length outer ST 24/40 joints, but with shorter necks. They are carefully designed and manufactured from No. 7740 borosilicate glass. Wall thicknesses are carefully controlled to provide the proper balance between thermal expansion and mechanical strength for greater shock resistance. The normal working temperature for these boiling flasks is 230°C. Adapter Cat.Nos. 1-8800, 1-8820 and 1-8825 are used to connect flasks with different size joints, thus allowing numerous combinations for diverse assemblies.