For all of you that want a usable Sight and don’t want to spend $400.00 to $600.00 to replace the White Ring Sight - THIS IS YOUR ANSWER!
See this YouTube review by TacticalExistence for a detailed examination of the REM-T3:
The Reticule Enhancement Module T Bar 3 (REM T3) fixes the problem that is inherent in the White Ghost Ring Sight of the P90/PS90 Weapons System. We all know in certain low light conditions or when aiming at bright or light colored backgrounds, the Ring Sight looses its sight picture. When that happens just turn on the REM T3, and you will get a sharp T bar sight picture.
The Reticule Enhancement Module (T-bar) 3GD is to be used as a back up to the Green Dot Ring Sight. Try to rely on the Original Sight when possible.
The Reticule Enhancement Module 3GD (REM T3GD) fixes the problem that is inherent in the Green Dot Ring Sight. We all know in certain low light conditions the Ring Sight looses its sight picture. When that happens just turn on the REM T3GD and you will get a sharp Green Dot sight picture.