ZipNFC ANTI METAL 30mm Round Disc/Tokens in BLUE ABS plastic, sticky 3M backing and very thin ferrite layer on the back. These are manufactured for business and used for commercial use so very strong and durable as well as having a strong adhesive applied. They also have an excellent reading distance. They are weather proof, waterproof, dust proof and can be placed on Metal surfaces so can be used outside as well as inside. These have a hole in the centre that enables you to screw or nail them to surfaces. They are rated as IP66.