Duracell Procell alkaline D batteries (1.5v). Procells were created for industrial applications, and are the alkaline standard in the entertainment industry. They have a seven year shelf life, they last longer than other alkaline batteries, they are mercury free, and they are rated to operate in temperatures from just below freezing to almost 130 degrees Farenheit. If alkaline batteries are what you want, then get the best. Sold in boxes of 12.