The Jagdtiger first appeared as two prototypes design by Porsche and Henschel respectively with the major difference being in the number of road wheels used. These were designated as Jagdtiger VI but later renamed to the more common designation of SdKfz 186. The tank destroyer featured the most powerful anti-tank gun of the war in the 128mm PaK L/55 - an armament that could quite literally shoot and defeat enemy armour before they were ever in range to fire back - and was fixed into position in the upper hull. Frontal armour took precedence and was nearly 10 inches thick. A crew of five to 6 personnel was needed to man the machine. The first unit to receive the Jagdtiger was s.Pz.Abt.653, as a replacement for the Elefant.