The kitten got spayed and I bought a donut collar from the store but I just eyeballed it instead of actually measuring so I got one that was too small. It's memory foam and expands out of the box so I can't return it.
We used it for the first night then I bought the next size up and washed this one.
XXS, fits neck circumference up to 5".
My goof is your gain, get it for a steal. They go for anywhere from $20 to $30, I paid $25.