Dumaco Garden Hose Washers.
The box says they are red, but they are green.
Status: Borrowed from Mr. OP’s toolbox, so no action required on my part. I have however mentioned that we don’t have a garden hose. Well, technically not quite true, there is the community garden plot, which has a complex system of hoses, but I doubt they are in need of these.
Kill-ratio: 30:3 or 10:1