These PYREX® Vista™ Short Neck Flat Bottom Boiling Flasks have full length outer glass 24/40 joints, but with shorter necks. The wall thickness of these flat bottom boiling flasks are controlled to provide greater shock resistance by balancing mechanical strength and thermal expansion. Designed to the specifications of ASTM E-1403, type I, class 4 — standard taper neck, short neck flat-bottom glass boiling flasks. Available in capacities ranging from 125ml to 1 liter; sold in cases of 12.