Thüringen was present during the fleet operation that resulted in the battle of Jutland which took place on 31 May and 1 June 1916. The German fleet again sought to draw out and isolate a portion of the Grand Fleet and destroy it before the main British fleet could retaliate. During the operation, Thüringen was the second ship in I Division of I Squadron and the tenth ship in the line, directly astern of the squadron flagship Ostfriesland and ahead of another sister Helgoland. I Squadron was the center of the German line, behind the eight König- and  Kaiser-class battleships of III Squadron. The six elderly pre-dreadnoughts of III and IV Divisions, II Battle Squadron, formed the rear of the formation.Shortly before 16:00, the battlecruisers of I Scouting Group encountered the British 1st Battlecruiser Squadron under the command of David Beatty. The opposing ships began an artillery duel that saw the destruction of Indefatigable, shortly after 17:00, and Queen Mary, less than half an hour later. By this time, the German battlecruisers were steaming south to draw the British ships toward the main body of the High Seas Fleet. At 17:30, the crew of the leading German battleship, König, spotted both I Scouting Group and the 1st Battlecruiser Squadron approaching. The German battlecruisers were steaming to starboard, while the British ships steamed to port. At 17:45, Scheer ordered a two-point turn to port to bring his ships closer to the British battlecruisers, and a minute later, the order to open fire was given.While the leading battleships engaged the British battlecruiser squadron, Thüringen and ten other battleships, too far out of range to attack the British battlecruisers, fired on the British 2nd Light Cruiser Squadron. Thüringen and Kronprinz engaged the cruiser Dublin, though both ships failed to score a hit. Thüringen fired for eight minutes at ranges of 18,600 to 20,800 yd (17,000 to 19,000 m), expending twenty-nine 30.5 cm shells. The British destroyers Nestor and Nomad, which had been disabled earlier in the engagement, laid directly in the path of the advancing High Seas Fleet. Thüringen and three other battleships destroyed Nestor with their primary and secondary guns while several III Squadron battleships sank Nomad. Shortly after 19:15, the British dreadnought Warspite came into range; Thüringen opened fire at 19:25 with her main and secondary battery guns, at ranges of 10,600 to 11,800 yd (9,700 to 10,800 m). The ship fired twenty-one 30.5 cm and thirty-seven 15 cm shells in the span of five or six minutes, after which Thüringen's gunners lost sight of Warspite, without scoring any hits. They then shifted fire to Malaya. Thüringen fired twenty main battery rounds at Malaya, also unsuccessfully, over seven minutes at a range of 14,100 yd (12,900 m) before conforming to a 180 degree turn ordered by Scheer to disengage from the British fleet.At around 23:30, the German fleet reorganized into the night-cruising formation. Thüringen was the seventh ship, stationed toward the front of the 24-ship line. An hour later, the leading units of the German line encountered British light forces and a violent firefight at close range ensued. Sometime around 01:10, the armored cruiser Black Prince stumbled into the German line. Thüringen illuminated the vessel with her spotlights and poured salvos of 30.5 cm rounds into the ship at point-blank range. The first salvo struck near Black Prince's rear gun turret, which appears to have been blown overboard. Thüringen fired a total of ten 30.5 cm, twenty-seven 15 cm, and twenty-four 8.8 cm shells. She was joined by three other battleships, and Black Prince was soon destroyed by a huge ammunition explosion. Around a half an hour later, Thüringen spotted what appeared to be a Birkenhead-class cruiser. She fired a starshell to illuminate the British cruiser and opened fire with her secondary guns. The ship was actually the destroyer Turbulent. Thüringen fired eighteen 15 cm and six 8.8 cm

Question: What size rounds did Thuringen use?
Answer: 30.5 cm

Question: Which German battlecruisers fired upon the Dublin?
Answer: Thüringen and Kronprinz