These are 6" long replacement cutting stones from Sun Valley Ski Tools' World Cup Stone Kit.
Made of premium green silicone carbide giving them superb cutting abilities.
A special bonding agent imparts a non-loading characteristic that makes these especially well suited for initiating the edge polishing process.
These whetstones are designed to be used wet and you'll see the best results with SVST's Secret Sauce Edge Polishing Solution,
Available in the following grits; 220 (coarse), 320 (medium), 400 (fine), & 600 (extra fine).
Stones sold separately and do not come with carrying bag as pictured above.