rain barrel, tank fitting, adapter plates

When you add a bulkhead tank fitting to a rain barrel, the smaller ones (e.g. 3/4" to 1") are generally not affected by the curvature of the barrel, but for larger than 1-1/4", the larger the adapter, the more if could become a problem. Bulkhead tank fittings are made for flat, not curved surfaces. For a 55 gallon barrel, the typical inside diameter is 22.5". These adapter plates add a flat surface on both the inside and outside for the bulkhead fitting to sit against. In the pictures, the t