Once the designer knows the desired LED size to fit a particular application, the next step is to select an LED of this size with the smallest possible viewing angle. Effective light pipe and LED matching occurs when the LED radiation pattern angle matches the acceptance pattern angle of the light pipe. This will help ensure that the light remains focused where needed and does not bleed into adjacent light pipes. Again, the viewing angle will vary from one application to another application. However, LEDs matched with light pipes typically have viewing angles less than 30° for surface mounted LEDs.