Gunsport's blog

REM-T3B USSS Sight Recticule Module

Fabrique Nationale (FN) replaced the white ring sight on the PS90 with a black ring sight.

The black ring sight is called the United States Secret Service Sight (USSS) or the USG sight. The black ring sight functions much better than the white ring sight in that you can see the black cross-hairs against white backgrounds; however, you cannot see the cross-hairs against black backgrounds or in low light conditions.The Rem-T3B solves this problem by illuminating the internal tritium sight.