There's certainly no lack of Hong Kong Triad films. I've seen the most prominent ones already, once in a while I find a lesser known one that has managed to escape my attention. Century of the Dragon is such a film, though considering all the talent involved I'm surprised I never noticed this one before.
Shing is a standout trainee who is sent on an undercover mission. He has to infiltrate the Hung Hing gang and befriend Fei Lung, one of their toughest leaders. Once there he learns that Fei Lung isn't actively participating in the Triad business he tries to inform the cops of the situation, but they won't listen to Shing.
With Louis Koo and Andy Lau in the lead you know performances will be on point. Clarence Fok isn't the most gifted director, but as part of the Hong Kong genre machine he does a pretty decent job. The film's a bit long and it offers nothing you haven't seen elsewhere, but the result is pretty solid Triad filler.