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 also be used with individuals who cannot open their jaws very wide. The Yellow Chewing Tube features a narrow stem with a 9.5mm outer diameter. The Red Chewing Tube offers a slightly wider stem with a 12.7mm outer diameter. This tube can also be used by children who respond to oral tactile stimulation or by adults with larger jaws. The Green Chewing Tube has been designed to increase sensory input through raised dots on the shaft. The shaft diameter is 15mm outer diameter. The Blue Chewing Tube is intended for adolescent or adult jaw sizes. It is the largest and firmest of the tubes. Adults with developmental disabilities and adolescents with autism or sensory integration disorders may prefer this larger size. Note: Chewing Tubes are not recommended for use with children under 7 months of age.