Sensibles Sensor Holder - Deluxe Starter KitSensibles Uiversal Sensor Holder Deluxe Starter KitContains: 12 Sensible Bite Blocks, 8 Medium And 4 Large Size 2 Each Anterior Posterior Aiming Rings 2 Each Anterior Posterior Positioning Bars 25 Comfee Sensor Sleeves Sensibles change on the fly with a simple push of a button and a quick reposition of the sensor. It's that fast and easy! Medium holds most size 2 and size 0 sensors. Large holds really big sensors.