That's the bottom cover for the Oppo Enco Buds W12, created using Voronoi pattern, it also has an loop to hook the headphones wherever you want. The earbuds can be charged with the cover on. ADVICES: Add supports, Scale it down a bit, like 98%-97%, to make it fit nice, If you're going to use the cover, use some glue or tape to secure earbuds to the cover.