It's a thin-walled socket ground down on the O.D. to fit into the I.D. of some bolt access holes that are comically only-just too small for a standard socket. I made mine with a sacrificial socket rotating on a power drill chuck against the surface direction (not opposite rotation where surfaces move alike) of a bench grinder abrasive stone, measuring occasionally with a calipers.
The MPP Lift Kit includes some substitute bolts that have a bolt head size for which a standard socket does fit into the access holes.
A local Subaru-focused shop installed the lift kit today in their first Tesla experience. 4 hours, all of which went smoothly except for more time than expected fixing the clearance for the front drive shafts. All good things to say about the kit and car.
Rides great! I think there might be slightly more wind noise, mostly from the more exposed stuff in the front wheel well. Getting alignment checked tomorrow.
I think some more full-coverage wheel well covers in the front might pair nicely against heavy snow buildup and such. I'm not a fan of the little tubes and things that are now very visible (but no more unprotected than before) with a clearer view above the wheels. There's even one view-through square hole in the front right wheel well that almost looks like an inspection point and goes pretty far in.