The Nisorpa graphite crucible contains 45% of C, 26% of AL2O3, 23% of SIC and 6% of SIO2 which has a stable chemical properties. The graphite crucible is more durable than the ordinary crucibles. Our graphite crucible is of high quality and convenient to use in the industry and lab. Chemical composition C: 45% AL2O3: 26% SiC: 23% SiO2: 6% Specification Thickness:13mm Outer Size: 128mm/5.04'' Diameter x 145mm/5.70'' Height. Inner Size: 102mm/4.015'' Diameter x 125mm/4.92'' Depth. Bulk Density: 1.71g/cm2 Apparent Porosity: ≤30% Refractory Strength: ≥8.55Mpa WARM TIPS FOR YOU 1. Let the crucible slowly heat up the first time you use it. 2. Avoid strong oxidation flame spray directly to the crucible when using the silicon graphite crucible. 3. Place the silicon graphite crucible in a dry place after use, avoid rainwater intrusion.