MT Mastera is a Finnish Aframax crude oil tanker operated by Neste Shipping. She and her sister ship, Tempera, are the first ships to utilize the double acting tanker (DAT) concept, developed by Aker Arctic, in which the vessel is designed to travel ahead in open water and astern in severe ice conditions. The two icebreaking tankers are used to transport crude oil year round from the Russian oil terminal in Primorsk to Neste Oil refineries in Porvoo and Naantali.