NXP NTAG213 On-metal / Anti-metal 40mm x 25mm tags with our NFC enabled logo. The front is white PVC with a glossy finish and a grey high quality ferrite sticky back that is 200 Microns. This sticker provides the best protection against metal interference and is really one of the thinnest anti-metal stickers around. These are manufactured for business and used for commercial marketing so very strong and durable as well as having a strong adhesive applied. The new NXP NTAG213 chip provides an excellent reading distance even on metal. They will work on any kind of metal surface.