It is a small LED that makes the light bulb light up and look very real, and bright, but it is made of acrylic, and not glass.       

 1)New Bulb Lamp with LED light and Keychain
2)The LED light can be any colors,such as:red,yellow, blue,white,green,rainbow,etc
3)Unit size: 30*52mm
4)With 3pcs AG3 cell batteries
5)Press bulb tail to switch on