The MasonLight is an energy-efficient LED lantern and an inventive way to re-use lids from home canning. "This is madness!" you say. No, this is science. The MasonLight has a "boost converter" circuit which allows a single AA battery to provide power. No expensive, hard-to-find lithium coin cells required. The MasonLight fits any wide-mouth mason jar and includes a drilling template if you wish to mount it elsewhere.