Reflections and I am not taking it as a wind up post its these daft little things that can cause problems and waste hard earned cash.
If you flying domestic your usually flying north south so one side of the cockpit gets the sun and the other doesn't. So one side wear them the other doesn't you get flashes coming from the the sunny side. And also you get twin beams on the instruments where the other person is looking. Apparently its even worse if the other pilot wears glasses because they cop the reflection off the inside of thier glasses.
PS to add I must admit I did do the swap, watch for ANR headset when the first job present topic came up with my family. Half the price of what they were planning to buy me but its been used every working day of my life since.