1, This card works the same as the normal IC cards, for 1K S50 standard. Only the Sector 0 Block Zero which is known as the Serial Number/Manufacturers Block(Chip CUID) could be programmed to any UID you want. 2, CUID card block 0 (UID's block) can be modified arbitrarily. 3, Card of the default password for 12 F, 4, CUID Support android phone NFC MCT modify UID. Colour:black Material:plastic Note:Common 13.56mhz rfid reader writer cannot write the CUID cards! NFC phone andriod App(MCT), acr122U,PM5/Pro,300CD,iCopy8, X100,Proxmark 3 support write CUID cards. Due to different batches, there may be differences in product appearance and printed text, which not affect use Package Contents: 20 x 13.56MHz CUID Card Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.