In some cases, some of the aligners in a set of steps will fit quite loosely or tightly, and can initially be difficult to get seated onto the teeth. This just depends on the treatment plan (how your teeth are scheduled to move) and how they actually move (which can at various times during the treatment be a bit slower or faster than predicted). Not to worry. This is normal. Using Chewies usually helps with this. If you are experiencing any problems, please always feel free to call our customer support experts.