The MEGA Live product includes two masks that are 7/8" long. These masks are designed to prevent double returns on your Live Sonar Image. This is especially important in Forward Mode.
Please take care to read the installation guide linked here.
Video Tutorial
Adjusting the Mask
The full length mask (7/8") is used for 50 and 60 degrees.
Shorten the mask to 1/2" for use with 40 degrees.
Image Examples
Below are images of the on screen results, with and without the mask. Without the mask you are likely to see double returns while in Forward Mode.