Sky Gem

The Sky Gem is is an optional upgrade for Sonic the Hedgehog in Sonic the Hedgehog (2006) and is one of the seven customized Gems that can be obtained in the game. It allows Sonic to perform the Gun Drive to fly long distances. When in use, the Sky Gem changes the appearance and colors of Sonic's Power Sneakers into a cyan pair of new shoes.

Location
In Sonic the Hedgehog (2006) the Sky Gem becomes available at the local shop, once the player clears Sonic's version of Kingdom Valley in the main story. It can then be bought for 10,000 Rings.