The winning bidders for the “Go on Stage with Christina” UltimateBid packages will be able to join the singer onstage for one song as a backup performer. Packages are available for 24 stops on the tour, starting with the August 21 date in Cincinnati and concluding with the October 19 show in Seattle.

Five separate auctions will offer a different prize for fans who don’t want to shake their booty with the pop princess. High bidders for the “Receive a Song Dedication from Christina” offer will get a special song dedication by Aguilera onstage during her performance. She’ll say that fan’s name and sing to the lucky winner. The package also includes front-row tickets and backstage passes.

The Aguilera auctions were the first marquee items featured on the UltimateBid page. Bidding for the “onstage” auctions started at $1,000, while the song dedication item started at $500. Net proceeds from the auctions will go to charity.