It is a delrin assembly consisting of a male part with the snap button and the other female part closing the button. Its main function is to connect, assemble elements between them. There is no slit on the tube part of these snaps.
Very easy to use but can only be used once so it is a single use (no reuse possible).
Installation by pressure then a simple quarter turn.
These natural POM snaps are mainly used to connect a color chart, a book etc...