This pushed the displacement up to 1,980 tons on the surface, 2,566 tons submerged. They were equipped with four torpedo tubes at the bow, two on either beam and another pair in a swivel mounting on the superstructure for night use. The swivel pair were later removed because they were prone to damage in rough seas. The K-class submarines were fitted with a proper deckhouse, built over and around the conning tower, which gave the crew much better protection than the canvas screens fitted in previous Royal Navy submarines.