The 12.8cm Kanone K-81 was designed as a heavy anti tank gun to match the heavy Russian armour such as the KV-1 and IS-2. Having faced the Russian 122mm guns, the Germans wanted something that would match its performance. Around 50 barrels and breeches were fitted to existing carriages with the K-81/1 using old French GPF-T carriage and the K-81/2 using the Russian A-19/ML-20 carriage. The Kanone K-81/2 was a design variation of the 128mm Kanone 44, Pak44 also used in the Jagdtiger.