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 the jaw very wide. It features a narrow stem with 9.5mm outer diameter. The Red Chewing Tube has a slightly wider stem with 12.7mm outer diameter, suitable for children 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, which has a 15mm outer diameter. The Blue Chewing Tube is the largest and firmest option, intended for adolescent or adult jaw sizes. It may be used by adults with developmental disabilities or adolescents with autism or sensory integration disorders. Chewing Tubes are not recommended for children under 7 months of age.