This is a vital piece to your AEGIS Windshield Repair Fixture (FIX2000). The Small Fixture Chamber (3/16", 4.8 mm) screws into the foot of the repair fixture and presses against the windshield for a tight seal on the impact point. The tip of the chamber holds a reusable quad ring for the seal against the windshield and the delivery of the resin. One seal is included as part of this chamber. If you need extra 3/16" replacement seals, please see part SBX2016.