RiteBrew Rubber Stopper - Size 10 - Drilled Go to amazon.com Related posts The 16 best carboy stopper Top recommendation for carboy bung Top 10 recommendation carboy cork FeatureDrilled to accept airlock or tubing.Top diameter: 50mm, 1.97 inches. Bottom diameter: 42mm, 1.65 inches DescriptionIt is a size 10 rubber stopper