If you're the owner pf a PWR modular bike light or flashlight, then this headstrap will allow you to convert it to a high power headlamp. Or if you have a PWR Bank from another product, just add this and a lighthead for the same result. QUICK START GUIDE Connect lighthead to headtorch - Plug the lighthead onto the front plate of the headstrap, aligning the PWR logo on the lighthead with the red button. Connect PWR Bank to headtorch - Slide the butt of the PWR Bank onto the T-Slot of the back plate of the headstrap. When you are happy it's centered, tighten the thumbwheel. Plug the cable cap onto the PWR Bank. The lighthead will flash once to confirm you're connected. Adjust the size of the headstrap. Angle of the lighthead can be adjusted manually. But to lock off the angle (for more rigorous activity), use the allen key provided. Operation - Once the lighthead and battery are connected, twist the lighthead and hold to turn on, twist and release to change the light mode. Hot tip: Your bike light or flashlight might not have the best modes for using as a headlamp. Download and use Knog's ModeMaker app to program what mode menu works best for you. WHAT'S IN THE PACK A. Head Strap. B. 2.5mm Allen Key. COMPATIBLE WITH PWR bike lights & flashlights. Note: Whilst large PWR Banks will work with the headstrap, it is heavy, so not an optimum setup.