Ivory tipped strikers Question

[WyoHunter]

What surfaces do they work best on? What material do you use to keep them conditioned? 

[gobbler336]

i haven't found a call that they sound bad on yet.  they tend to raise the pitch a bit on every call.  after a while they develop a dark ring around the very tip where they rub the call i hit it with scotch brite to remove the discoloration but haven't had one get really slippery yet.