The main difference between SleepPro Standard (Easifit) and SleepPro Custom (S2 or AM) is the way they fit in your mouth. SleepPro Standard comes as a one-size-fits-all mouthpiece that uses a boil-and-bite method to mold to your teeth. SleepPro Custom (S2 or AM), on the other hand, is custom-made to fit your teeth perfectly, using an impression of your teeth. This ensures a more comfortable and effective fit. While both devices are designed to treat snoring and mild to moderate sleep apnea, SleepPro Custom (S2 or AM) is generally considered the better option for those who want a more personalized and comfortable fit.