A Shaped Light Bulbs
"A" type bulb shapes are standard house hold light bulbs. The number after the bulb shape is the number of eighths of and inch in diameter. For non-imperial measured bulbs the number following the bulb shape is the number of centimeters at the widest point of the bulb.
Standard bulb sizes include A19 for imperial measurements and A60 for a slightly smaller metric measured bulb.
B and C Shaped Light Bulbs
B shaped bulbs are also know as Candelabra Light Bulbs. The have a bulged base that tapers to a rounded or pointed tip. In some bulbs the tip is bent giving the slight look of a licking flame. C shaped bulbs are similar to holiday lamps.
These bulbs are common in chandeliers, night lights and lower wattage applications such as holiday string lights.
Typical bases for B and C shaped bulbs are E12 in North America.
Typical bases for B and C shaped bulbs are E12 in North America.
PAR Light Bulbs: PAR16, PAR20, PAR30 and PAR38
PAR light bulbs utilize a parabolic mirror or reflective surface to focus the light. For LEDs the PAR designation is used to define the shape, as most do not have a reflective lower surface due to the directive nature of LEDs.
Common PAR lamps include the PAR20, PAR30, PAR38 and PAR42, though many other sizes exist. These bulbs come in various beam angles that result in spot and flood lamps.
This shape is very similar to the R shape and in some cases the PAR and R are interchangeable as shapes for LED replacements.
| PAR Size | Diameter in Inches |
| PAR-16 | 2 |
| PAR-20 | 2 1/2 |
| PAR-20 | 2 1/2 |
| PAR-30 | 3 3/4 |
| PAR-36 | 4 1/2 |
| PAR-38 | 4 3/4 |
| PAR-46 | 5 3/4 |
| PAR-56 | 7 |
| PAR-64 | 8 |
Source:
http://www.eaglelight.com/category/lighting_tutorials.bulb_shapes/
