3 Pounds of MJR Tumblers Premium Quality Extreme Polish 12,000 Grit Sub Micron Aluminum Oxide Rock Polishing Powder. for Unparalleled Quality and Performance. A Disabled and Veteran Owned Company! 3 LB 12000 Grit Step 4 is up for auction in Industrial & Scientific. The current bid is $4.00, 91% below the $42.50 MSRP, in As Is condition. This auction has ended — similar items appear in live auctions regularly.