Dubro gas stoppers are brown... Sullivan gas stoppers appear to be black (from looking at the Sullivan part numbers on Tower Hobbies website)...
http://www2.towerhobbies.com/cgi-bin...?&I=LXFU84&P=7
Versus the while glow stopper
http://www2.towerhobbies.com/cgi-bin...?&I=LXFU80&P=7