3D printers; 3D printing pens; abrading inserts for use with machines; abrading machines; abrading tools for use with machines; abrasive belts for power-operated sanders; abrasive bits for use with machines; abrasive discs; abrasive disks for power-operated grinders; abrasive disks for power-operated sanders; abrasive grinding wheels [machines]; abrasive grinding wheels [tools for machines]; abrasive instruments [machines]; abrasive instruments [tools for machines]; abrasive sharpening stones...