Any standard base (regular household) light bulb will fit into these strings. The maximum wattage per socket is 25 watts. All our bulb options are listed on our Medium Bulbs Only page. Our most popular option is our 11S14 Bulbs. They are 11 watts and seem to give off the right amount of ambience in most situations. Many customers are investing in LED Bulbs. They last much longer and use significantly less energy than the regular incandescent bulbs.