The vessels of the SX157 design are a part of the ALP Future class. Service speed is 13 knots, while their top speed is 19 knots. With a fuel capacity of more than 3,500t, they can tow at full power for 45 days, sufficient for non-stop Trans-Atlantic/Indian, Pacific Ocean towing operations without fuel calls. The vessels are constructed by Niigata Shipbuilding & Repair, Japan.

The vessels were developed especially for this project in close collaboration between ship designer Ulstein Design & Solutions AS and ship owner ALP Maritime Services, the latter a subsidiary of Teekay Offshore Partners L.P.

A vessel of this type typically tow oil rigs, or FPSOs, from the building yards to the installation site at the oil field. Additionally, these vessels are outfitted with DP2 and anchor handling capacity in order to assist during the installation/hook-up phase for the towed objects. The vessels are 88.9 metres long and 21 metres wide.