The Mercer 545100 is a 5 100 Grit PSA Gold Aluminum Oxide Disc. The Mercer 545100 is a premium gold stearated non-loading disc. The disc is resistant to heat and moisture with great grain adhesion. The gold stearated disc has a longer life and can be changed quickly. The aluminum oxide disc can be used for giving excellent finish and fast cutting also. The primary use of the disc is for finish sanding of plastic filler, rough featheredging paint, fine featheredging paint, sanding putties and final primer/surface sanding.