LC133
Unlock addition skills—with a simple turn of the key! Our self-correcting locks and keys make learning addition facts to 20 a breeze! Kids simply pick a key…solve either one of the two problems printed on it…then find the lock with the answer. If they’ve solved it correctly, the key will turn and the lock will open—for instant reinforcement! Set includes 20 locks and 39 keys; locks measure 3 1/4".