Q: How much weight does this rear kit save on a Model S Plaid?

It removes 16lbs of unsprung rotating weight, about 38% less than stock. Factory rear rotors weigh 41lbs combined; these are 25lbs. Because that weight is both unsprung and rotating, cutting it sharpens suspension response and helps efficiency at the same time. The rotor itself is a 365 x 28mm carbon-silicon carbide unit, the same diameter as factory, so the gains come from material and packaging rather than a size change. For a lower-cost rear option that keeps the OEM caliper, see our Large Sweep rotor and pad set.