[agent323]

Will the M6 light/laser combo work on the new/04 P99's?

 

[extremist]

Not without an adapter that GG&G sells. You need this:
M5 to M3/M6 Conversion Kit
Because Walther, in deference to their partnership with S&W went with the M5 compatible rails rather than the "everyone else" M3/M6 compatible rails.

James