I play lead in a 17 piece big band and swear by them. Need to perfect them...slot down to pedal C and below, Refreshes the embrocure, aligns the corners, relaxes the middle of the chops where  the tone is produced helping to get the set for the high stuff. Also use them regularly before, during and at the end of practice. I have received great benefit from them..Many top player endorse them and use them in their literature. Claude Gordon, Jerome Callet. Paul Cacia whom I talked to explained their value as did Glenn Stuart when I took lessons from him.Anyway, just one person's opinion. They are a valuable part of my routine and have helped me a lot.