Remember all of the flashlights that used 3 AAA or 3AA's & a bright white LED with no resistor; a few had a switch to bypass a low value resistor as batteries aged. I still have some, never lost a LED. LED's were mostly not pre selected for Vf. I converted several cheap 3-AA pen cell lights to bright white LED's with 3 N cells & spacer- no resistor. Sold for $ 13.; now 9 LED's for free at Harbor Frt.