The 1" x 6" balsa strops are mounted on aluminum blanks.. The idea behind balsa wood as a strop medium is that a balsa surface is soft but rigid. When you apply compound you are creating a custom honing surface. The compound particles embed and stay in place while you are working, and itís easy to sand the surface clean and flat when the compound is spent. This provides a cheap and easy way to experiment with a variety of different honing compounds where you can mix and match with low cost and good results.