Serial.print(F("Card UID:"));
for (byte i = 0; i < uid->size; i++) {
    if(uid->uidByte[i] < 0x10)
        Serial.print(F(" 0"));
    else
        Serial.print(F(" "));
    Serial.print(uid->uidByte[i], HEX);
}
Serial.println();

Card UID: A6 74 E6 2B