Thoughts on tea strainers like this?

I’m considering something like this for taking loose leaf tea to work (there are many better things to use when space and time are less of an issue, the reason I’m considering this is because it’s slender enough to fit neatly in my lunchbox and should work well enough with the paper cups my workplace provides).

Has anyone used these? Is it worth a shot or a complete waste of effort and money? Is there something else I should be considering instead?

I’m also considering disposable loose leaf tea bags, can anyone recommend a good reliable brand?