Do rim protectors fit staggered wheels?
Staggered, on these factory charts, means the rear tire is wider than the front. It does not mean the rear wheel is a different diameter. A protector is still matched to the inch number on each tire.
Does a wider rear tire change the diameter?
Tesla's Model Y owner's manual lists the Performance tires as 255/35R21 in front and 275/35R21 in the rear. The wheels are 21 x 9.5J in front and 21 x 10.5J in the rear. The 21 is the same. The width is not.
The six-seat sets work the same way. At 19 inches, Tesla lists 255/45R19 in front and 275/45R19 in the rear, on a 19 x 9.5J front wheel and a 19 x 10J rear wheel. At 20 inches, the tires are 255/40R20 in front and 275/40R20 in the rear. The plain 18, 19, and 20 inch rows are the same size at both ends.
What do you match on the listing?
Match the number after R. In 275/35R21, that number is 21. A listing that says 21 inch is talking about the diameter, not about 255 versus 275. Those first numbers are the section width in millimeters.
Width still matters for the lip. AlloyGator's fitting page starts with the size printed on the sidewall, then the suitability gauge. A wider rear rim can change how far the lip sticks out. The gauge is their check. It is not a promise that one ring suits both ends. The diameters in this shop are 19 inch, 20 inch, and 21 inch.
What if the two tires print different diameters?
Then you have two diameters, and you match each one. Tesla's Model Y table does not split a factory set that way. Front and rear share the inch number, even when the rear tire is wider.
If you are comparing cars, rim protectors by car lists the factory diameters Honda, Hyundai, Ford, Toyota, and Tesla publish. Find your wheel size is how to read the number already on your tire. The Model Y and Model 3 tables, including the Model 3's own staggered 20 inch row, are in rim protectors for a Model Y or Model 3.
The 35 and the 40 in those Model Y sizes are the sidewall ratio. Do rim protectors work on low-profile tires? is the note on a 35 or a 40. Rim protectors on alloy wheels is the note on the metal the ring sits against.