RFID hard pvc tag is made of hard plastic such as pvc , pet or another biodegradable materials . It also can contain LF ,HF and UHF frequency chip .  They can water proof because fully encapsulation with our any spaces even flat surface .  For working purpose , you can requested adhesive backside or ferrite (anti-metal layer) backside  .Round coind shape and another irregular shape ,customized printing and personalization are available .