those things for sublimation
These popular things are made for sublimation, but can also be used for vinyl as well. They come in a set including the outside , a two sided adhesive piece as well as the aluminum piece to be sublimated. They include 3M adhesive to be attached to your phone.
Double sided adhesive tape is used to stick the insert onto the holder. The cap on the holder has groove recessed for placing the insert in.
Note* the back side of the aluminum disk for subbing is aluminum look, the front has a layer of protective film on it.