This 150 grit wheel measures 4" in diameter with a 1/2" thickness.  Use on a polishing motor with a 1/2" arbor.  An innovative abrasive material for fast grinding and superb surface finishing! GRX consists of aluminum oxide dispersed in a unique elastic bond. Cuts a bit slower than silicon carbide yet imparts a very smooth surface finish – each grit yields a much higher finish than expected. Grinds platinum, gold, silver, steel and aluminum without clogging. Prevents metal surfaces from becoming scorched during processing. Very long-lasting. Can be easily dressed using an old file. Made in Japan.