This is a support pin for adjustable shelves. You typically get extra pins together with a bookshelf or other piece of furniture. These pins work perfectly as replacements and since they are quite small, you can print a couple of them in an hour.
They are designed to fit my bookshelves and fit snugly in the 0.185" holes. The specified peg diameter in the STL file is actually 0.19", which I have found through experimentation gives the best fit for my printer and my shelves.