Was exploring some really dark and pitch black caves.
I had an AA and a 3D maglite, both incandescent. My mate had a Led Lenser L7 and bought X21R! This was less than 2 years ago. Needles to say, his lights blew my lights away. My lights could lit up close to nothing compared to his lights.
I was not willing to pay the price of X21R in order to get lots of lights, nor was I interested in it due to size/weight. Came across BLF and the rest is history..