The only adjustable bite block that holds most digital sensors in both the anterior and posterior positions. One bite block per patient for an entire exam. Sensibles change on-the-fly with a simple push of a button and a quick reposition of the sensor. Medium holds most Size 2 and Size 0 sensors. Large holds really big sensors. Aiming rings and alignment arms provide for super-accurate x-rays. Kit contains: 2 Large and 2 Medium Bite Blocks, Positioning Arms (1 Anterior, 1 Posterior), Aiming Rings (1 Anterior, 1 Posterior), 25 Comfees Deluxe Sensor Sleeves