12 Shape and Diameter of Common Lamps
Aaron Lee
In the lighting field, lamp bulbs are identified with a letter code to identify the overall shape of the bulb, and a numerical designation that represents the widest diameter of that bulb in eighths of inches (1/8).
For example, a T8 fluorescent lamp would have a tubular (T) shape and a diameter of 8 eighths of an inch, or 1 inch, while a T12 would have a diameter of 12 eighths or 1 and 1/2 inches.
Lamps may also include voltage or power ratings, which can be used to make sure that any lamp installed in a lighting fixture will not exceed its rated value of current and reduce the risk of fire or electrical hazards.
EX: A multifaceted reflector, or MR 16 lamp, has a diameter of 2 inches or 16 eighths of an inch.
