The full details of the contract are unknown, but Shams Charania of The Athletic and Stadium reported it's a "multiyear deal."
Culver is widely considered a top-five prospect in the 2019 draft. Bleacher Report's Jonathan Wasserman projected him to the Cleveland Cavaliers with the fifth overall draft pick.
The 20-year-old played a starring role for Texas Tech in 2018-19 as the Red Raiders finished runners-up to Virginia. He averaged 18.5 points, 6.4 rebounds, 3.7 assists and 1.5 steals.
Culver is the second 2019 draft prospect to sign an endorsement deal with an apparel company. Ja Morant announced May 27 he opted for Nike.
Of course, most fans are waiting to see where Zion Williamson lands. Williamson is the consensus No. 1 player on the draft board, and legendary marketing executive Sonny Vaccaro told ESPN.com's Nick DePaula the Duke star could be the target of "the biggest bidding war ever done."