Flex Style Repeater Sticker
 
These are Super thin .24mm thick and on a 3m Sticky back. Can be placed anywhere to extend or repeat a 13.56Mhz NFC Signal. 28mm circle. Sold individually or in packs of 4, 8, or 16.

NOW with Options
After many requests we now have two options available.  One with the classic stem logo, and one that is stealthy and black.  Under the 3m tape backing the logo is still applied. (This is intentional in the case of guerilla placements, if removed someone can go to the github and see the project and what these devices are for)
 
What a Resonance Repeater?
A resonance repeater circuit is designed to resonate at a specific frequency. These are tuned to resonate at 13.56mhz. What this means is when it is placed within a 13.56mhz field it will repeat the signal.
 
NFC and RFID high frequency devices typically operate at this frequency. This device can be used to extend the normal operating range of the field that would normally generate.
 
 
How can i use this?
 
These amplifiers can be used in projects that would require you to scan NFC devices through objects where the reader isn't powerful enough by itself to pass the signal through. You could place this item on one side of the obstruction, and the reader on the other, and it will help to amplify the field that is generated so you can couple with the chip to the reader.
 
 
How much distance does it add?
 
It varies with device. Keycards seem to get about double to triple the original range. Smaller devices like fobs get almost double. RFID chips you will see about 5-9mm of read distance.
 
 
Use Cases these have been used for:
 
Place in between a Phone and Phone case to get more reliable NFC Read distance Place in a wallet to read Keycards through multiple cards within the wallet
Place in Gloves to read Implants in hands
Will help fix NFC Issues with NothingPhone 2 as documented here.
 
Where can I place these?
You can place them on any reader or device that operates on 13.56Mhz (most High Freqency NFC Devices). The Dangerous Things Community has a Wiki that documents best placement areas sorted by device here: Placement Wiki