DFRobot Relay Shield  V2.1 is a completely new design which is capable of controlling 4 relays at a time.

Shield of relays for Arduino, with 2 channel mechanical relays and with 2 channel MOS switch , providing an easy way for applications low and high voltage control. 

8 relay module with ports " NC " means " Usually connected to COM " and ports "NO" means " Usually open to COM ".