Bluetooth 4.0 NRF51822 Core Board, Small Factor – Waveshare

Features

Onboard chip: nRF51822
Communication distance (open outdoor@1M data rate): 30m
Frequency range: 2.4GHz
Operating voltage: 2.0V ~ 3.6V
Operating temperature: -40 degree ~ 85 degree
Dimension (PCB): 17.0mm x 20.8mm
Expansion pinheader: all the I/Os except P0.26 and P0.27
Antenna: onboard antenna
Weight: 0.002 kg

Resources
Wiki

Core51822 (B) Expansion Headers