On the 50-55 pound bows I shoot they aren't necessary, in fact, my current primary shaft ,rivercane (I finally found a great patch of the 15ft stuff!) is supposedly prone to splitting and I have not yet had that problem, wrapping around the nock with sinew is all that is necessary for me. However, I like the looks of horn inserts and think that they are very useful for high-poundage bows.