The 3"/50 caliber gun (spoken "three-inch fifty-caliber") in United States naval gun terminology indicates the gun fired a projectile 3 inches (76 mm) in diameter, and the barrel was 50 calibers long (barrel length is 3 in × 50 = 150 in or 3.8 m). Different guns (identified by Mark numbers) of this caliber were used by the U.S. Navy and U.S. Coast Guard from 1890 through the 1990s on a variety of combatant and transport ship classes. The gun is still in use with the Spanish Navy on Serviola-class patrol boats.