RayTools Ceramic Ring 20.6mm Diameter 8mm Thread 3D
https://www.fabtechshop.com/shop/xp-cer00-0006-120572008b-rt-1229000261-raytools-ceramic-ring-20-6mm-diameter-8mm-thread-3d-2795
https://www.fabtechshop.com/web/image/product.template/2795/image_1920?unique=f5006a4
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Out diameter: 20.6mm
Thread size: M8
Ceramic height: 13.5mm
Cutting type: 3D