Retro 2

The Retro2 is designed to replace the filament bulbs in an Oldham or Speleo-Technic cap lamp. It can be powered by most standard cave light batteries. The design uses 2 x Seoul P4 LED's giving a total light output of over 200 Lumens. Both LEDs are fitted with 10° optics. Care is needed to ensure the cap lamp is well sealed as water ingress will destroy the light.

http://mineexplorer.org.uk/ledlighting.htm