There are two versions of this under development: one by the Inner Sphere, the other by the Clans. The Inner Sphere version weighs one ton per location. The Clan version weighs a half-ton per location. Both types take up one critical slot in each protected location. CASE II works like standard CASE, preventing an explosion from damaging the center torso of a 'Mech if installed in one of the side torsos, the more advanced version venting more of the damage out of the 'Mech away from the internal structure. Unlike the classic Star League era standard CASE, Inner Sphere CASE II also mimics the standard Clan version's ability to be installed in the arms, preventing any explosion in the arms from affecting the local side torso.
When an internal explosion occurs, CASE II reduces the damage to the Internal Structure of the installed location, making it take only one point of damage (with a chance for a critical hit). If the explosion is in a side torso, the rest of the damage is applied to the rear armor of the location. If there is no further armor, the remaining damage is negated out the open rear of the 'Mech. If the explosion is in an arm, the rest of the damage is applied to the armor, and negated away from the 'Mech. CASE II also reduces the chance of critical hits taking effect due to the redirected damage.
Unfortunately, CASE II does not protect the pilot from taking damage from ammo explosions, so standard rules apply in this case.
- Tactical Operations, p. 299, "CASE II"