Professor Foam&trade; 6 Remington O-ring Barrel Seals for Model 1100 12, 16 or 20 Standard Gauge 11-87 12 Ga 16 Ga 20 Ga From This is the one you have been hunting for. Manufactured, tested, packaged & sold by Professor Foam. High-grade Genuine DuPont Viton O-rings replace old, worn, or cracked rings to provide a proper seal and restore gas system reliability. Resolve blow back issues with 12, 16, 20 gauge gas ports for Remington 1100 & 11 87 Shotgun. Will resist most solvents used to clean firearms. DuPont Viton has a high tolerance to compression and operational at an extreme heat of 316C(600F) down to a freezing -54C(-65F).