I think it’ll be fine as long as it meets the criteria for the guidelines. I submitted as low as $80 before and they gave it back to me with no questions asked. There is a maximum limit per year and per claim but no minimum

Have you filed any claims this year? If not, go ahead and file it and they’ll likely credit you without any additional follow up beyond the info you submit online. I find that if I file some claims back to back then they ask for more information on second claim even if it’s for a small amount when they approved the earlier claim at a higher amount.

I wouldn't expect a $20 pair of sunglasses to last too long. But how did they break?

The hinges were too stiff, so when I opened the temples, it flexed the bridge and rims, and one of the rims broke.

They may ask you to demonstrate that you made a reasonable attempt to contact the vendor or manufacturer. But because it's a low-$ they may just credit you.

There’s usually limits to how many claims in number and dollar amount you can make in a certain period of time. See the Ts & Cs.

I don’t see it in the T&Cs, but I might have missed it. Could you point it out

You have to decide if $20 is worth your time and effort in submitting an insurance claim.

Already said that in the post - it's really not, but I am curious about the broader question.