Two additional Schwarzlose M.07/12 anti-aircraft machine guns were mounted atop the armoured cupolas of each ship's rangefinders. Each ship had two Škoda G. L/18 landing guns, and two Škoda SFK L/44 S guns for use against small and fast vessels such as torpedo boats and submarines. Each ship was also fitted with four submerged torpedo tubes, one each in the bow, the stern, and each side. Each ship usually carried twelve torpedoes. The "Tegetthoff"-class ships were protected at the waterline with an armor belt which measured thick in the central citadel, where the most important parts of the ship were located. This armor belt was located between the midpoints of the fore and aft barbettes, and thinned to further towards the bow and stern, but did not reach either. It was continued to the bow by a small patch of armor. The upper armor belt had a maximum thickness of , but it thinned to from the forward barbette all the way to the bow. The casemate armor was also thick. The sides of the main gun turrets, barbettes, and main conning tower were protected by of armor, except for the turret and conning tower roofs which were thick. The thickness of the decks ranged from in two layers. The underwater protection system consisted of the extension of the double-bottom upwards to the lower edge of the waterline armor belt, with a thin plate acting as the outermost bulkhead. It was backed by a torpedo bulkhead that consisted of two plates. The total thickness of this system was only , which made it incapable of containing a torpedo warhead detonation or mine explosion without rupturing. In the spring of 1909, Montecuccoli sent an officer from the Naval Section of the War Ministry to Berlin in order to obtain input from Alfred von Tirpitz on the design of the "Tegetthoff" class. The Imperial German Navy had conducted gunnery and torpedo tests and concluded that, "The angle between [the] armored deck and belt armor should be as flat as possible", and that "The armored torpedo bulkhead should be angled inwards, the second longitudinal bulkhead outwards. The distance of the torpedo bulkhead from the outer plating should be raised from 2.5 to 4 meters." While Popper adopted several of Tirpitz's suggestions regarding the external layout of the belt armor for the "Tegetthoff" class, the internal modifications put forward by the Imperial German Navy were not implemented.