the rfid is very sensitive. i receaved 10 pcs inside , 4 of them didn't work.
Excellent chip, it works fine even though it is small in size, the only problem is that it is not sealed with epoxy, it is very fragile, I wasted 3 chips when testing... then I made sillicon sandwich to keep the chip and coil together, you can see on the pictures, writing to chip is working fine, fast shipment, good seller