Includes: 50 PCS Replacement O-ring for 12, 16, 20ga Standard Remington 1100 or 11-87 Dimension: 15/16" ID,1-1/16"OD,1/16"Thickness Fits all Model 1100 and 11-87 12-gauge Shotguns - O-Ring Barrel Gas Seals Seals for Remington 1187 11-87 1100 12 ga O-Ring Seals