‎1.97 inches

【Reptile Essentials】Appropriate amount of UVA and warm light produced by the light radiation for reptiles environment to provide hot sun drying temperature. Improving reptile appetite and body color deposition, which is good for promoting food digestion. 【High-Quality Material】The reptile lamp bulb uses a plating process to make sure anti-oxidation & explosion-proof. and use a vacuum glass tube to extend lamp life. 【Easy to Install】The heat bulbs is simple and easy to install, just screw it into a standard E27 screw base. The reptile lamp could be used for turtle, lizard, frogs, snakes, and various amphibians in the container.