Armed with a 35 mm Oerlikon KDA autocannon, it is meant to defend surface combatants against various types of maneuvering aerial targets such as anti-ship missiles, unmanned aerial vehicles, conventional and rotary-wing aircraft, It can also engage surface and coastal targets.

On December 19, 2012, NCBR signed an agreement with the consortium consisting of the Military University of Technology (leader), Polish Naval Academy, Bumar Elektronika S.A. (currently PIT-Radwar S.A.) and ZM Tarnów S.A.[1] First, a prototype version of the system, named OSU-35 was to be developed and tested.

The results of the prototype's trials and the experiences gained during its development would serve as a basis for designing a new, production variant of the system, the OSU-35K.

In 2013, the first renders of the OSU-35 were unveiled, showing a conventional design with the gun mounted in a fully enclosed, angular turret.

The OSU-35 system consists of four major components: the AM-35 (Armata Morska - Naval Cannon) gun-turret armed with the KDA autocannon, the ZGS-158M (Zintegrowana Głowica Śledząca - Integrated Tracking Head) optical sight fitted, the main fire control station and the emergency fire control station.

[7] On November 12, 2022, the AM-35K turret was mounted on the ORP Mewa minehunter to test the interchangeability of the systems between different ships of the class.

[10][11] In mid 2023, the prototype of the system completed sea trials on board of the ORP Albatros, after which it was accepted into service in September.

[15] The armament of the system in all of its variants is a single 35 mm Oerlikon KDA autocannon produced by HSW under a license obtained in 1995 for the now cancelled Loara SPAAG program.

[16] The gun is gas operated, fires at a rate of 550 rpm and is belt-fed from both sides by two 100 rounds ammo racks.

The dual feed feature of the KDA autocannon makes it unique among other guns of the KD family as it allows to use two different ammunition types (usually FAPDS and ABM) and switch between them depending on the type of the target, which increases the flexibility of the system when compared to those based on the KDC (such as the Gökdeniz, Korkut or Göker) or the KDG (Millenium, Skynex or MANTIS).

The AM-35 (Armata Morska 35 mm - 35mm Naval Cannon) turret is visually similar to that of the Oerlikon Millenium system, with the gun being placed centrally in an enclosed, angular housing.

[20] The ZGS-35K sight is maded mostly out of carbon fiber consists of a daytime and thermal cameras as well as a laser rangefinder and an IKZ-50P IFF system.

[21] The development of the airburst ammunition started somewhere in the 2nd decade of the 21st century in relation to the San and Noteć programs meant to replace the Navy's 57mm land-based air defense systems.

[3] Together with a high-frequency laser rangefinder, the programmable ammunition allows the system to engage fast moving and maneuvering targets at ranges up to 3.5 km.

On the Project 258 minehunters, the RSKO-35K console is mounted on the ship's bridge, which allows the operator to visually identify the targets for the bow-mounted AM-35K turret.

[26][27] The SA-35 (Samobieżna Armata 35 mm - 35mm Self-propelled Cannon) is a land-based VSHORAD system with counter rocket, artillery, and mortar (C-RAM) capability, meant to defend stationary targets such as critical infrastructure, cities or SAM batteries.