This Pack Of 12 Incandescent Decorative Chandelier light bulbs are 40 watts with a torpedo shaped straight tip and crystal clear finish. The average rated lifetime is 1500 hours. They produce around 385 lumens, have a candelabra (E12) base (Which is 12mm in diameter) and will work with a dimmer. They are ideally used in Chandeliers, ceiling fixtures, portables, vanities, and sconces, as well as other household lighting fixtures or fans. The basic design of the incandescent lamp has not changed much since the late 1800s, when Thomas Alva Edison successfully produced the first operational electric light bulb. The filament inside an incandescent lamp must be protected so that oxygen does not reach it and cause it to evaporate on contact. Most incandescent lamps are either vacuum-sealed or gas-filled. Incandescent lamp filaments are made of tungsten. Tungsten is a metal that can operate at very high temperatures without evaporating too quickly and resulting in early lamp failure. Incandescent filaments only convert about 10-Percent of the energy used into visible light, so it is necessary to use a material that can withstand extremely high temperatures. Most lamps use a coiled filament design, which has been found to be stronger and deliver better performance.