Kinstone Bag

From Zelda Wiki.org

The Kinstone Bag is an item received in The Minish Cap after completing the Deepwood Shrine and returning to Hyrule Town. It is a bag in which you keep all of your Kinstones. The Kinstones you find are only halves, so you must find people who have another matching half and fuse them in a process called Kinstone Fusion. As you collect more Kinstone pieces, the bag will grow and begin to bulge.

After completing the Kinstone Fusion sidequest, Tingle will change your Kinstone Bag with a trophy.