Snapdragon double is a competitive double after the first three players bid three different suits. 

• including your partner  16+ HCP at 1 level or 19+ HCP at 2 level;

• exactly doubleton in partner's suit;

• 4+M or 5+m at 1 level or 5+M or 6+m at 2 level in the unbid suit.

W N E S

1♦

1♥ 1♠ X*1 2♠

3♣ 3♠ P P

4♣ P P P

*1 Snapdragon Double (5+♣, 8+ HCP)

W N E S

1♥ 2♣ 2♦*1

X*2 2♥ P 3♦

P P P

*1 1X-(Y)-2Z forcing

*2 Snapdragon Double (5+♠, 7+HCP)

The Snapdragon double is forcing for one round. In response to a Snapdragon double, overcaller's rebids are natural.