The were an early Russian design of torpedo gunboats. The ships measured 60.2m (197.5feet) long with a beam of and a draught of . They had a displacement of 420t and had a complement of 65 officers and ratings. They were propelled by one shaft powered by a vertical triple expansion engine fed steam by two Ioco boilers rated at 3500ihp. The Kazarskis sported a single funnel. They had a maximum speed of 21kn and could carry of coal for fuel. They were initially armed with six 3-pounder (47 mm) guns and three 1-pounder guns. The Kazarskis were also equipped with two 15inches torpedo tubes. One was fixed in the bow while the other was deck-mounted and could be trained at targets.
The vessel underwent a series of modifications during her existence. In 1907 Posadnik had her 3-pounder guns replaced with two /40 calibre guns. In 1910 the ship was rearmed with two guns, two 57 mm guns, two machine guns and the bow torpedo tube was removed. In 1911, Posadnik underwent another change, having the bow 75 mm gun swapped out for a 4inches/60 calibre gun. In 1917, the second 75 mm gun was swapped out for a 4-inch gun.
Posadnik was constructed at the Schichau shipyard in Elbing, Germany. The vessel was laid down in 1891 and launched on 13 April 1892. During World War I, Posadnik was used as a despatch vessel for the Baltic Fleet. During the Bolshevik Revolution, Finland declared independence from the Russian Empire in 1918. The basis for the new nation's navy were a series of former Russian vessels abandoned during the revolution in Finnish waters. Posadnik was taken over in March 1918 and renamed Klas Horn for a a 16th-century admiral. The ship was stricken in 1937 and broken up for scrap in 1938.