These are lowering links of various lengths that replace the stock links that came with your air suspension. You'll find a link at each corner of the car. Select a new link length to adjust the ride height of the car at that corner. The links in this project are for the rear of the car. See another project for the front links, which are 20mm shorter and a different design that is necessary to fit up front.

Print the links out on ABS plastic using Cura or your favorite slicer, I found thicker layers (0.3mm) make a stronger product. You will need to print 2 links, one per side of the car (rear). Typically, you select 2 links the same length for both sides of the rear. Unless you find your car was poorly calibrated, you can select different lengths to remove the difference and get a more consistent height at that end of the car.

These are fixed length links for rear suspension, in various lengths, the longer the length the lower the suspension will go. 70mm is the stock length of the links that come on the rear of the Model S.

The number in the file name is the distance from ball-to-ball (center).
68mm is actually a shorter than the Tesla stock rear link and this will raise the car.
70mm is stock height.
72mm is lower ride height than stock.
74mm is lower yet
76mm is lower than that
78mm is the lowest ride adjust adjustment

Note, before getting your car recalibrated by Tesla service, install the 70mm links back on the car. When the car is returned to you, put back on your favorite height links.

There's an optional "locking cap" you can push onto each link end after installing the link onto the car.

See the thread on teslamotorsclub forum

https://teslamotorsclub.com/tmc/threads/3d-printed-lowering-links.78336/

If you don't have a 3D printer, I can print links for you in ABS plastic for $10 per link, so $40 for a set for the car - you pick lengths (I recommend starting with a set that is +4mm or +6mm over stock length, front and rear). This price includes shipping to anywhere in world. Send a private message to scottm on teslamotorsclub forum.