Works as intended...for the ones I've used.
I received 12 of these extension straps in the package and on initial inspection, they all appear to be in good condition. They use a snap/button to attach the strap to your face covering ear loop and a fastener (like on a jacket cord) to tighten the strap to your head. I've only used a few of the straps, but the ones I've used so far all work to keep my face covering from slipping off my face/ears. They do look a little funny on the back of your head because the strap is fairly long (to accommodate different head sizes), so after you pull the strap tight against your head, it looks like you have a little pony tail sticking out from your head.
Rating: 4 stars