K.I.T.T. and K.A.R.R. are armored with "Tri-Helical Plasteel 1000 MBS", or Molecular Bonded Shell plating which protects them from almost all forms of conventional firearms and explosive devices. They can only be harmed by heavy artillery and rockets, and even then, the blast usually leaves most of the car's shell intact and only damages internal components. The shell protects every part of the car including the tires. As a result, K.I.T.T. could act as a shield for explosives by driving over bombs and suppressing the blast. A laser is also capable of damaging the alloy, however the shell can only withstand a maximum of 2 shots before being neutralized.
The shell also protects against fire and electricity; however, it is vulnerable to some potent acids and at least one formula was made to completely neutralize the shell. Long exposure to seawater can weaken the shell.
The shell provides a frame tolerance of 223,000 lb (111.5 tons) and a front and rear axle suspension load of 57,000 lb (28.5 tons).
The shell is actually a combination of three secret substances referred together as the "Knight Compound". It was developed by Wilton Knight who entrusted parts of the formula to three separate people. Each individual knows only two pieces of the formula, ensuring that any two of them could make more of the Knight Compound in an emergency situation and that no one person would be able to make it.