Most of Steiner's spas are on cruise ships, including 133 Steiner spas on the largest vessels in the fleets of Royal Caribbean (NYSE:RCL), Carnival (NYSE:CCL), NCL, and Disney (NYSE:DIS). It also runs 48 resort spas for hoteliers like Hilton and Marriott (NYSE:MAR), but the cruise ships provide far more revenue and give Steiner its biggest competitive advantage. Even when companies like Princess have tried an in-house approach to manage a spa, they find themselves ultimately hooking up with Steiner again.