Spa jet plug / bung

https://www.youtube.com/watch?v=NyYP5UVp-x0&feature=youtu.be
Probably of little use to anybody else but perhaps it may be,please let me know if you use them, for anything.
These are small bungs that I use to bung up the jets in my home spa jacuzzi thing in order to squirt water through just one at a time to clear them out. If I know I wont be using it for a few days I don't like the idea of my last baths water hanging around inside the tubes. Likewise if I haven't done this before not using it I most certainly do it before using it next time.
I use water pressure to feed the water in using the input adapter, I didnt bother with a thread it didnt need it.
These are 16mm, scale accordingly, they have an extra edge to ensure you can extract them even if they have a tight fit. They are designed to be quick and cheap in terms of plastic,not to be stylish or classy :)