Assuming that you are talking about open reed guts, allpredator.com has Yeller Dog inserts. They are the best I have ever used. There are 3 models to choose from.
The YDD3 is a pure distress call
The YDD2 is a hybrid distress/howler
The TD1 is a full bore, loud, howler
My person preference is the YDD2. I just switch the reeds (included) to make either distress or howler
.All Predator also has JC reeds for closed reed calls.