The used Olympus FR-WR Wireless Radio Flash Receiver lets you remotely trigger and control flashes. Key features include:

Remote Flash Trigger. You can use the Olympus FR-WR Wireless Radio Flash Receiver to remotely trigger and control flashes using 2.4 GHz radio transmission via an Olympus FC-WR Wireless Radio Flash Commander (not included). It has a 98.4-foot receiving range and can operate on one of 15 channels within 3 groups.

Easy Setup and Control. This receiver has a top shoe for attaching a flash, a bottom locking cold shoe, and two rear dials for simple channel and group selection. You also get a PC sync terminal for wired pairing with strobes. The FR-WR uses two AAA batteries (not included).

High-Quality Build. Like Olympus OM-D-series cameras, this receiver is splash-, dust-, and freeze-resistant, so you can use it in inclement conditions.

Compatibility. As of January 2019, the Olympus Wireless Radio System is only supported by the Olympus OM-D E-M1X / E-M1 Mark II / E-M1 / E-M5 Mark II and PEN-F.