This is an adapter to attach a flexible plastic gutter to a COSWA 55 Gallon Rain Barrel that I purchased from www.upcyclerainbarrel.com.
This adapter keeps the flexible plastic gutter in place so that all the water goes into the rain barrel. It attaches through the existing screws in the top of the barrel, and requires gutter screws to keep the flexible gutter in place.
I made this from PETG due to the outside temperature swings.