FLAT BOTTOM BOILING FLASK SET, LONG NECK, BORO, 4pc -PKG190 • Four piece starter set (100, 250, 500, & 1000ml) flat bottom boiling flasks with reinforced tooled top • Made of special Borosilicate glass (Bore 3.3) that has excellent chemical and physical properties and  >80% silica content • Stable structure with great mechanical strength and high resistance against chemical attacks; withstands high thermal shock • ISO 9001:2000 certified