I've been hunting for 19 years using several different calls. I have always returned to mouth calls. Brian's calls have worked well for me from call shy Utah coyotes to  cats in South Africa. These calls are the best quality of any I have seen. With that said they work very well!
I was in South Africa last year on a plains game safari. With every intention to call predators every chance I had. With the animals that we had on our list, we weren't left with much time to call predators. The professional hunter we were with had never called before in his life. The first time we went out with calls in hand was a cold September night. Out into the brush we went. We called for a short time when the first eye appeared. Small spotted genets slowly stalked our way. To small to shoot, we watched until it slowly crawled off. I looked over at our PH, eyes opened wide you could see the wheels turning. He then asked me if I thought it would call in a lion. Without hesitation I replied "yes it would". After a couple calls and only small cats to respond we called it a night. We had three different species of cats come in, none of which where large enough to ship home to the US, we gave them a pass. 
After a few short lessons on how to call, I reluctantly left one of these call with our PH. He had every intention to go and call lions with it. If you are a predator hunter at all, these are the calls to have. I wish I would have had these calls when I started calling. I know I would have had better success. These calls work. Thanks Brian your calls are awesome. 
                 -Bryan Sorensen