Just for your information : in France and in Belgium, it is very common that the 2♣ Roudi (from Roudinesco) is played. It is very simple and very effective : 1m 1M 1NT 2♣ = at least invit with 5M or not 2♦ : mini, 2 cards in M 2♥ : mini, 3 cards in M 2♠ : maxi (14), 3 cards in M 2NT : maxi, 2 cards in M with the inference that : 1m 1M 1NT 2NT = transfer to 3♣ cause you can't play 2♣ anymore. Alain