Passage: Pre-dreadnoughts carried guns of several different calibres, for different roles in ship-to-ship combat. The main armament was four heavy guns, mounted in two centre-line turrets fore and aft. Very few pre-dreadnoughts deviated from this arrangement. These guns were slow-firing, and initially of limited accuracy; but they were the only guns heavy enough to penetrate the thick armour which protected the engines, magazines, and main guns of enemy battleships.The most common calibre for the main armament was 12-inch (305 mm), although some ships used smaller guns because they could attain higher rates of fire; British battleships from the Majestic class onwards carried this calibre, as did French ships from the Charlemagne class (laid down in 1894). Japan, importing most of its guns from Britain, used 12-inch guns. The United States used both 12-inch (305 mm) and 13-inch (330 mm) guns for most of the 1890s until the Maine class (not to be confused with the earlier Maine of Spanish–American War notoriety), laid down in 1899, after which the 12-inch gun was universal. The Russians used both 12 and 10-inch (254 mm) as their main armament; the Petropavlovsk class, Retvizan, Tsesarevich, and Borodino class had 12-inch (305 mm) main batteries while the Peresvet class  mounted 10-inch (254 mm) guns. The first German pre-dreadnought class used an 11-inch (279 mm) gun but decreased to a 9.4-inch (239 mm) gun for the two following classes and returned to 11-inch guns with the Braunschweig class.

Question: Which guns did Japan used, the ones they imported from Britain?
12-inch guns.