[E13]
The Petzl E13 was designed for the Petzl Zoom headlamp. If you purchased the Zoom without an adapter the zoom only runs on Flat 4.5volt batteries, this is a great alternative. The adapter fits snugly into the battery compartment of the Petzl Zoom and allows you to use 3 standard AA batteries (not included) instead of the 4.5 volt flat battery.