Bulb Nomenclature by Shape

Each glass bulb is classified with a unique code which determines its size and shape. The shape of the bulb is denoted by a letter (or letters), and this is followed by a number which gives the maximum diameter. In most countries of the world the diameter is stated in millimetres. However in the Americas the number represents the maximum diameter in eighths of an inch (e.g. an A19 bulb has a diameter of 19 eighths of an inch, which is 2.375" or 60mm).

The key for the letters associated with each shape follow: