The reaction tube with high vacuum valve is used in air-sensitive Chemistry. With high vacuum valve at Top, allows the gas to be evacuated or filled with gases.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.