Per Lockheed Martin’s press release:
Lockheed Martin’s concept for a crewed lunar lander is a single stage, fully reusable system that incorporates many of Orion’s flight-proven technologies and systems. The lander would accommodate a crew of four and 2000 lbs. of payload on the surface for up to two weeks while returning to the Gateway without maintenance or refueling on the surface.
See how Lockheed Martin’s lunar lander concept might work in the video below: