All the WEVO differential side cover products are designed to combat the increased loads that are experienced in the Porsche transaxles as a result of the high grip levels avaialble from modern tyres - even on original size rims.
The "seperation force" of the bevel gear configuration in the differential is most directly effected by grip levels. The differential side cover is in direct control of this force. By making the cover stiffer, the CWP (Crown Wheel and Pinion) gears are arragned in their design configuration over a wider rang e of loads, alleviating heat from friction and wear from misalignment.
Add to this the fatigue that 40 year old high components have endured already and there is a compelling argument to install a new side cover during any transmission rebuild for a sports purpose Porsche 911, 1965 - 1986.