Pappy ( Jack Lewis) made me a glass / slate call combo a few years back. Out of all the pot calls I have ( tons of them - all custom call makers) this one is my "go to" call in the woods.
Glass on one side, slate on the other. A few different strikers and it's like having 4 different calls... I don't like carrying a bunch of junk / calls , so this works great for me. This call really knocks the birds down...
