There is a strong trend for modern knives to be made with increasingly more abrasion resistant steels. This allows the edges to last longer and to attain higher levels of sharpness for a longer period of time. The downside is that if a knife is more abrasion resistant it is also harder to sharpen.
Traditional abrasives like Aluminum oxide and Silicon carbide just aren't hard enough to do the job adequately. CBN is harder.
CBN is Cubic Boron Nitride. While it works well on all steel, CBN solves the problem of keeping your abrasion resistant steels razor sharp. It is second only in hardness to diamond and preferred for use on tool steels, powdered steels and for anyone requiring a high performance edge.
It is available in a number of grit sizes measured in microns or grit - 16 micron is 1000 grit, 8 micron 2000 grit, 4 micron is 4000 grit, 2 micron is 8000 grit, 1 micron is 16,000 and .5 is 35,000. You will find the 4 micron grit finer than the original edge on Bark River knives. The 8 and 16 micron compounds are used to restore a worn edge and the 2 micron grit will bring your edges to an extremely fine level of finish perfect for use on outdoor knives, kitchen knives and most everything else needing a sharp edge. Progressing to 1 micron and .5 micron will bring your edge to the 'ultimate level' of sharpness.
The CBN grit or particles are in a water soluble emulsion, somewhat similar to a hand lotion. This is a custom formulation engineered for Bark River. This makes it perfect for use applying it on leather strops.
To apply it, I use a disposable glove, put just one drop on the leather strop and smear it around. The glove lets you spread it further. Continue until you have covered the strop with a thin coat. One drop gives about 6 square inches of covering. It absorbs into the leather quickly. If a glove is unavailable, a clean hand will do. You need very little - a thin coat will do. Each coating will last you a long time.
Just add more as needed over time to the strop to recoat. Just a couple drops will be more than enough to sharpen 30 or so knives at least. Some report getting a lot more use than that.