This opening promise 5-5 in majors or minors. In Norway this convention is only allowed in 1st and 2nd division, and in the national team finals. The reason is that the rules in Norway state that you have to define at least one suit if the opening bid is weaker then 16 HCP. Personally I love this convention, and think it's great.
3: Preference
3: Preference
3: Invitation in heart
3: Invitation in spade
3NT To play if minors.
4: Forcing.