Durofelt is a company that sells 100% wool felt. As most are aware, wool does not burn all that easy and especially when lubed. The felt wads will protect the projectile from the powder charge, seal the gasses better in the barrel giving more power they claim, and some even feel it helps to reduce leading. I do know that in many circumstances they will improve accuracy.

They can also be used with patched roundball especially if you notice the patches are getting damaged badly when fired....