A rechargeable headlamp. The MH10 is a versatile light. It uses a nowadays common 18650 cell (included) as its power source so in heavy use you can just buy as many extra batteries as you need and take them along.
Ledlenser, MH10 Rechargeable Headlamp, LED Light for Outdoor Use
Ledlenser MH10 Rechargeable Headlamp - £66.99
LEDLENSER MH10 600 Lumen LED Rechargeable Headlamp with Focusing Optic MH10 - The Home Depot
Ledlenser - Ledlenser MH10
Ledlenser, MH10 Rechargeable Headlamp, LED Light for Outdoor Use
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LEDLENSER MH10 High Power LED Rechargeable Headlamp, 600 Lumens Includes Free Ledlenser Running Sport Neo H4 Headlamp