Teether Bite Stick Chewing Tube Sensory Chew Biting Aid Oral Muscle Training The Yellow Chewing Tube offers a smaller stem size for chewing and can be used by individuals who cannot open their jaw very wide. It features a narrow stem with a 9.5mm outer diameter. The Red Chewing Tube has a slightly wider stem with a 12.7mm outer diameter. This tube is suitable for children who are receptive to oral tactile stimulation or adults with a larger jaw. The Green Chewing Tube is designed to increase sensory input through raised dots on the shaft. The shaft has a 15mm outer diameter. The Blue Chewing Tube is intended for adolescents or adults with larger jaws. It is the largest and firmest of the tubes. It may be used by adults with developmental disabilities or adolescents with autism or sensory integration challenges. Note: Chewing Tubes are not recommended for children under 7 months of age.