The Medium Quiver is an item available in Skyward Sword. It allows Link to carry 10 additional Arrows when it has been placed in his Adventure Pouch. It can only be received by upgrading the Small Quiver at the Scrap Shop in the Bazaar. In order to perform this upgrade, Link needs 5 Amber Relics, 3 Dusk Relics, and 3 Monster Horns. The cost is 50 Rupees.
The Medium Quiver can be upgraded at the Scrap Shop to the Large Quiver, which can hold 15 extra arrows. This upgrade requires 3 Dusk Relics, 2 Monster Horns, 1 Goddess Plume, and 1 Golden Skull. The price is 100 Rupees.