This connector sleeve joins two pool noodles together. You slide a noodle into each end of the sleeve, and that holds them fast. The sleeve is 14 cm long and has a through hole with an inner diameter of 65 mm.
That turns loose noodles into a longer string or a ring, instead of having to manoeuvre two separate pieces all the time. It is the kind of thing someone in the water immediately finds a use for.
The material is foam, the same as the noodles themselves are made of, so the sleeve is light and bends along with them. The colour in the photo is yellow.
Handy if you already have a few pool noodles at home and want to do more with them. You get a single sleeve - pool noodles are ordered separately.