Double Barrelled Stayman

Over 1NT, 2C and 2D ask opener for a four card major.
2C is not forcing to game. 2D is game-forcing. Over
2D, opener rebids

*2H or 2S to show four
*2NT with 4-4 in the minors
*3C, 3D, 3H, and 3S to show 5 of that suit
*3NT with exactly 4333 with 4 in a minor

This convention is used in Precision Club