The CED M2 Chronograph Set (ED-M2) is a well known, well used and fantastically successful product; a well establish and widespread chronograph rig that both real steel and Airsoft shooters use, primarily those testing IPSC and other competition guns (it can read 50 to7000 FPS).
This package is an add-on kit for the M2 CED set, it adds struts and a reading assembly that makes use if infra red LEDs instead of the basic factory ones. The IR reading screen offers the same performance but the alteration of light frequency means that it is not plagued by issues of poor lighting as other ones are.
If you have a CED M2 Chronograph set then picking up one of these is such a good idea it is almost mandatory.