Size:Capacity of 25mL This multi-neck flask has two standard taper ground joint on the Centre neck and the side angled neck. With 2 necks having the same joints Laboy glass flasks are heavy wall designed, made by hand-blowing to ensure uniform wall thickness, made of high-quality borosilicate glass and annealed at 800 degree Celsius, can be heated directly in an open flame and can withstand typical laboratory thermal variations in Chemistry processes like heating and cooling.