In this case, it is made of rubber or silicone, and the temple slides into the hole as shown in the photo, preventing the glasses from falling out and getting lost. Ideal for children or the elderly. I've never used it, I bought it for a friend's daughter and never used it after all.
I invite you to look at my other sales on Clozen as I can give you a good price for buying a lot. I want to get rid of everything and make some space in my wardrobe.