3 Charles Daly 12 Gauge Semi-Auto O-Ring Barrel Seals This is the one you have been hunting for. Manufactured, tested, packaged & sold in the U.S.A. by Mallard Armory. High-grade synthetic rubber O-rings replace old, worn, or cracked rings to provide a proper seal and restore gas system reliability. Resolve blow back issues with gas ports for Charles Daly 12 GA Semi-Auto Shotgun. Will resist many solvents used to clean firearms. Material has a high tolerance to compression and operational at an extreme heat of 316C(600F) down to a freezing -54C(-65F).