The "Out-And-Back" is the section of the Equinox Marathon, Ultramarathon and Relay course that begins at Ullrhavn Summit at mile 12.4, goes west along the summit ridge of Ester Dome to the Turnaround (approximately mile 14.75), then returns by the same route to Ullrhavn Summit at mile 17.1.
This section involves ascending four summits on the way out, and the same four summits on the return. Most of this part of the course is on gravel road/mining road. This section can often have many puddles and will likely be rutted in places.
The Ultramarathon has its own "Ultra Out-And-Back" section beginning at mile 28 (approximately) and ending at about mile 34. This out-and-back section ascends fairly continuously from Ballaine Road to a turnaround point above the KUAC dish on Bender Mountain, then returns by the same route. Most of this segment is on trails, with a fairly significant section on a rutted, gravel road (Herreid Road).