They are made from 96% purity Aluminum Oxide (Al2O3) which of course is Alumina. Generally the balance of composition for this purity Alumina material is of Silicon Dioxide (SiO2) which is Silica. This material has very high hardness, very high stiffness, very good corrosion resistance to chemicals at high temperature, and very high refractory ness or use temperature.

COUNTERBORED BUSHING. You are buying a Lot of Six (6)1.070″ Long x 0.750 OD High Purity Large Alumina Ceramic Thick Walled Sleeve Bushing. They are made from 96% purity Aluminum Oxide (Al2O3) which of course is Alumina.