Product details: Chip: t5577 or uid chip Frequency: 125kHz or 13.56MHz Inner diameter of ring: 17mm, 18mm, 19mm, 20mm, 21mm, 22mm Color: Black Material: zirconia ceramic + epoxy resin Packaging: an RFID smart ring Read write: read and rewrite Note: This product is a new factory product, only one chip（125khz or 13.56mhz）125kHz is null instruction (rewritable), 13.56MHz default instruction (read-write).