Whatever size battery fits in the tube 26650—21700 etc then make a dummy spacer out of aluminum for the rest of the tube —- maybe your light will be able to run on 4.2v —otherwise just buy some new lights
Whatever size battery fits in the tube 26650—21700 etc then make a dummy spacer out of aluminum for the rest of the tube —- maybe your light will be able to run on 4.2v —otherwise just buy some new lights