With joint. Cotton is usually used to contain drying agent.

Made of borosilicate glass

Made by hand blowing

Be Made From G3.3 Borosilicate Glass

Annealing Point ------560℃

Linear Coefficient of Expansion------ 33×10-7/℃

Softening Point------820℃

Proglass glassware is 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.