The "Iron Duke"-class ships mounted a main battery of ten 13.5 inch (34.3 cm) Mk V(H) guns in five twin gun turrets, all mounted on the centreline. Two turrets were placed in a superfiring pair forward ("A" and "B" turrets), one turret amidships—the "Q" turret—directly after the two funnels, and two in a superfiring pair aft of the rear superstructure ("X" and "Y" turrets). The gun houses used were Mk II turrets that weighed 600 tons (610 tonnes) and allowed for depression to −5° and elevation to 20°. Despite this, the range dials on the gunsights at the time of construction were graduated to 15 degrees; super-elevating cams and prisms to allow the full elevation of the guns to be used were issued some time after the Battle of Jutland. The forward and aft gun turrets could train 150° in either direction from the centreline, while the "Q" had a much more limited range. It could engage targets on an arc from between 30° to 150° from the centerline on either beam of the ship.