Although the tags for metallic surfaces to be useful, they are not. I wanted to equip a mobile hotspot with NFC, but even if the tag is located on the battery of the hotspot, it is no longer recognized by the Nexus 7 and Nexus 4. Also on other metal surfaces do not work the day. Probably it is because the NFC antenna of the device is significantly larger than the day, so that despite the ferrite shield the signal is reflected by the metal. Ideally, you could get the shielding separately for cutting would be.
