NRF24L01 + 2.4Ghz wireless module.
The NRF24L01 + is a 2.4 GHz transceiver with a built-in hardware protocol (Enhanced ShockBurst ™), made for ultra-efficient wireless applications. The nRF24L01 uses the 2,400 - 2.4835GHz band to communicate. This module can be accessed with the Serial Peripheral Interface (SPI). The configuration registers of the module can also be changed via SPI.
The NRF24L01 + module is the upgraded version of the NRF24L01, this module also has a "long-distance mode" with 256kbps, in addition 2 ground and 2 3.3V pins have been merged.