After the Trak 4x4 chains went out of stock at the Tesla Store, I purchased a set of AutoSock traction devices, part number 698, for my MX with 20" Continental rear tires. I got mine from Amazon. The attached photos show the practice installation. I have not been in snow deep enough yet where I needed these (the M+S Continentals perform quite well by themselves) so I don't have any actual use data to share. What I can say is that these go on the tires easier than any set of chains, including split chains, that I've ever used. In the photos you see: 1. The plastic carrying case with the AutoSocks and instructions printed on the outside. 2. Starting at the top of the tire, the sock wraps around the tire like a fitted sheet. You try to wrap as much of the tire as possible. NOTE: It is much, much easier to first raise the suspension to Very High. 3. Move the car forward or backward one quarter of a tire rotation. 4. Wrap the remaining tire. 5. Driving even a short distance will auto-center the sock. Like all chains, the manufacturer states the speed is limited to 30 MPH. They also caution that use on dry roads will accelerate the fabric wear. But, I have these for emergency use. They take up relatively little space in the trunk or frunk, They have very positive reviews for their increased traction. They cost 1/5 of the price of approved chains. And, like I said above, I found them very easy to install. I'll update this thread when I get a chance to use them in snow.