Three great options for all-weather floor mats for the Model 3 are from TuxMat, 3D MAXpider, and ToughPro. The best set for you depends on your priorities for coverage vs aesthetics vs value.
First up are the TuxMats. These have a unique look that isn't necessarily my favorite, but they are very well-designed and constructed and give excellent coverage. They fully cover the carpet around the center console and also the rear seats. If I lived in a snowy climate they would be my choice, hands down.
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Next up are the 3D MAXpider Kagu mats. Kagu is the name they use for this carbon fiber-ish look that fits in really well with the design of the Model 3 interior. They also offer a Classic line of carpeted mats and I expect they'll offer the same for the Model 3 eventually. These mats look like they will provide good coverage, will be the most durable, and the most attractive.
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Finally, we have the ToughPros. These are basic protection for a reasonable price. You can get a full set to cover the interior and both trunks for less than the price of the other two options. These aren't my favorite look or coverage, but I can't deny the value.
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Check out the video for more info and the links to pick up a set for yourself.