Danielsan
Enlightened
It depends on what is bright? A normal keychain light with those round and flat batteries can be bright too and super small. But for me it must be over 150 Lumen for sure and that Eiger thing is not so small in my mind because the Batteries ist uses are pretty long. AA and AAA Batteries are too long, i think a light with CR2 batterie would be the best like the Mini CR2 4 sevens or the Lummi lights.