Strop 'N' Polish [professional] is a great gift set for professional and intermediate sharpeners.

Four-sided leather strop is used at the very end of the sharpening process to remove the remainder of the burr from the blade. This four-sided leather stop has 2 suede ("coarser") sides, and 2 smooth ("finer") sides of the leather. The idea is to leave one grainer and one smoother leather "naked", without any polishing compounds, and use the other two to apply differently granulated polishing pastes. The principle of using a four-sided leather strop is pretty much the same as with sharpening stones. We start stropping on the coarser leather and finish on the finer, smoother leather.

Koyo polishing paste (smaller chunk) will help with removing the burr and adding a high polish to your newly sharpened edge. Simply rub this green block on the surface of the leather strop until the leather is slightly green in color. 

Here's a short video from our Instagram on how to apply Koyo paste to the leather strop: How to apply Koyo polishing compound