I have so far trimmed every call I have purchased in order to get a good seal. Everyone's mouth is different, so you may need to do some modifications to get the call to fit right. It is going to take some time to figure out what the right fit is and to become proficient at it. I would buy a couple of the exact same call, and try to trim them up to your liking, leaving one of the calls in its original form so you can always compare it.