Bulb Types: A bulb designation consists of a letter(s) to indicate the shape and a figure(s) to indicate the approximate majoy diameter in eighths of an inch. Bulbs are measured through their greatest diameter in eighths of an inch. Thus, an F-15 bulb is a flame shape, 15/8 of an inch or 1 7/8 inches in diameter.
Filament Types: A filament designation consists of a prefix letter to indicate whether the wire is straight or coiled, and a number to indicate the arrangement of the filament on the supports. Prefix letters include: C (coiled) - wire is wound into a helical coil or it may be deeply fluted; CC (coiled coil) - wire is wound into a helical coil and this coiled wire again wound into a helical coil.
Base Types: Typical screw base is shown. One lead-in wire is soldered to the center contact and the other soldered or welded to the upper rim of the base shell. Base shells are typically made of brass or aluminum. ANSI designations are in parentheses.