The Clover Box is a music box with a see through top that can open and close with the four leaf clover. At the side there is a handle that can be turned to play the music. Inside are four hearts representing each Cure's signature color with a crystal in the middle that spins around in a circle when played.
With the Clover Box the Cures can perform the attack Lucky Clover Grand Finale, warn the Cures of Nakewamekes, and return Chiffon back to normal when she becomes Infinity.
You can see the box in Fresh Pretty Cure!'s 2nd ending, H@ppy Together.