Aluminum nitride ceramic Seal Rings for high frequency heat treatment Made of precision ceramics, with good sealing effect and insulation of aln ceramic rings, it can be used in high frequency porcelain heat treatment. Product details: 1.Material: Aluminum Nitride . 2.Function: insulating device ceramic. 3.Type: Ceramic ring. 4.Color: Gray. 5.Can be customed: yes, please provide drawings for specific products.