The T4K (Trainer for Kids) is most effective in early mixed dentition for tooth eruption guidance and correction of myofunctional habits. Tooth channels and labial bows guide the erupting/developing dentition into correct alignment, while the tongue tag and lip bumpers treat myofunctional habits. Base to 1st molars only. Starting (Phase 1) is soft (Silicone) and finishing (Phase 2) is harder (Polyurethanel)