Notice that the connector before order.
Cooling Fan: 4.0 x4.0 x2.0 cm
Compatible with: Synology RS818RP+ RS818+ RS819 RS816 Disk Station
Package include:
1 X Cooling Fan
Synology Fan
Spare synology fan for your NAS system. Can be used as an additional fan to prevent your system from overheating and working beyond working capacity.