At the recommendation of forum members here i bought this Strop: Illinois Razor Strop 2.5" x 23" Imperial Russia with Handle - Knifecenter.com

It just came in the mail. If you look at it it has 4 different canvases that could be used for stropping. I am of course familiar with the leather. But what's the purpose of the other 3 canvases, and when would I use them?