Umbrella Hat
In theory, this is a great idea i.e. a hat that collapses and so you can stuff it in your pocket.
However, keeping your head dry is much better served with a normal hat or even the hood of a rain mac which can scrunch down to much smaller units.
This is a novelty hat only.
The hat as shown collapses umbrella style, but in lieu central pole has several braces which fit into an elasticated band which grips to your head in a very uncomfortable way, that probably would not keep your hat in place in a gust of wind.
I can see myself chasing this hat across a beach if there is a breeze.
On the plus side the wide brim does provide extra sunshade and a little shoulder protection from the rain, so might be of some use, but unless I want a laugh I will pack a bucket hat for emergency use.