These are Peek Sheets.

Thin, sturdy, adhesive-backed reflective card that can be stuck to almost anything! Cards, deck boxes, phone cases, wallets, Air Pods... you name it. Turn any ordinary object into a DIY peek device perfect for mentalism, card magic and on-the-go miracles.

Set-up in 30 seconds. Perform for years.

4 Peek Sheets are included with every purchase; simply peel away the blue protective film, remove the white adhesive backing & cut to preferred size