Ive got a little 3'' slate over glass in a cherry pot that Pappy made for me. The pot is a flip over style pot to where I can use the glass soundboard as a striking surface and it is a little nasty raspy call full of bird. I called up 8 hens this past fall and shot the brood hen in the head while using that call. The slate is perfect for making soft to mid range yelps, tree yelps, clucks, and the glass on the underside is brutal for making long distance yelps that reach out there and touch. I run it with a hickory/pecan striker and also an osage striker and it rocks.
Pappy can make any kind of call your looking for, and he may be able to offer some direction according to the sound your looking for. It really depends on what kind of sound your looking to make.
Ben
