Quartz collars and discs are made of 99.90% pure quartz fibre with very high strength, low thermal expansion and high elongation at the breaking point. Quartz collars and discs also have excellent resistance at high temperatures. Quartz collars and discs are recommended for temperatures up to 1050ºC (1922ºF).
ALF collars and discs are made of continuous alumina-silica fibre consisting of 70% Al²O³ and 30% SiO². These collars and discs retain their strength and flexibility after operation in high temperature environments. Because they are boron-free products, there is no risk of negative effects resulting from the release of gases.
By comparison, some competitive products contain boron and are, therefore, unacceptable for semiconductor applications. ALF collars and discs are recommended for temperatures up to 1395ºC (2543ºF). ALF collars and discs are made of 7 micron fibre to ensure superior flexibility.