SainSmart SIM900 GSM/GPRS Function Module Adapter for Raspberry PI, Arduino Quad-Band 850/ 900/ 1800/ 1900 MHz GPRS multi-slot class 10/8GPRS mobile station class B Compliant to GSM phase 2/2+Class 4 (2 W @850/ 900 MHz) Class 1 (1 W @ 1800/1900MHz) Control via AT commands (GSM 07.07 ,07.05 and SIMCOM enhanced AT Commands)