HiLetgo 125 KHZ EM4100 RFID Card Read Module RDM630 (UART) Compatible Arduino Installation is more convenient: direct serial read, all pins lead to electronic building blocks interface Higher Sensitivity: Advanced RF Receiving Line, Embedded Microcontroller Design, Efficient Decoding Algorithm More compact size: the full version of the design optimization, rational wiring, practical superior performance Support external antenna.Maximum effective distance up to 50mm. Support EM4100 compatible read only or read/write tags.