Geekworm Raspberry Pi 3 Model B/2B Sim800 GSM/GPRS/SMS Board Quad-band Add-on Expansion Board for Raspberry Pi This is a SIM800 GSM/GPRS add-on V2.0 board for Raspberry Pi 3 Model B/2B; Quad-Band, Supports 850/ 900/ 1800/ 1900 MHz; Class 12 GPRS multislot; 3.3V DC operation level digital;UART interface. For more details, please refer to wiki: http://www.raspberrypiwiki.com/index.php/Raspberry_pi_Sim800_Expansion_Board