71003 M 4 Layer cover fits my 83 MB CDT just fine.
It's good to 190 inches and the MB is 187.5 inches.
Reasonably flexible and easy on/off.
Also a 4 year warranty.
Beats the $200 covers some of my neighbors have.

I should have bought the one for a compact car. I thought of my five passenger car as mid size, especially after seeing some of the offerings (midget?). But I already owned a motorcycle cover from the same people and it has been really great. I like the car cover and I think I could recommend it. Though I do think that you should consider your car rather smaller than you probably think of it. I'm using two ropes to tie mine on and that works rather well. It's more secure in the wind in either case. Using this cover can prevent the excessive sun damage that Arizona sunshine does to a good car.

I purchased this cover for my Chrysler because of the birds and trees around my driveway. A good wax job can be ruined by crap and sap in one day. I ordered the mid-size because the 300M is a mid-size. The box says I should have ordered a full-size but the mid-size fits like a glove, almost like it was custom-made for my car.
At first I thought having the bag attached to cover was a bad idea, but it does help quickly identify the inside rear of the cover and facilitates putting the cover on. And the bag easily tucks under the cover.
Putting it on is a little tricky with a rounded roof line. I line it up from the rear and pull forward from the front keeping it in the middle of the roof.
I know from previous experience that this type of material can tear when you try to remove it if it gets wet and freezes to the vehicle.
I gave it 5 stars for the great fit...

Three years ago I bought a cover from Costco for 39 dollars and it was a wonderful, thick, soft cover. I thought I would step up this time and buy this "4 layer deluxe cover" for a little more money. What a mistake. Four layers? Where? The material is paper thin, and stiff as a board. I guarantee this cover will scratch a nice paint job. I held the cover up to the outside light, from inside my garage , and it lit up like a cheap lamp shade. They actually supply a security cable to stop theft. Why?.....nobody in their right mind would steal this cover. The people that gave this piece of junk 5 stars, must not know what a decent cover looks like. I should of taken my old cover to a laundry, and washed it. You have been warned.

I highly recommend this durable and effective car cover.

The background is I travel a lot and didn't want my car sitting exposed to the elements in an airport parking lot for three days each week.

When I looked at options I wanted something which:

1. Was well made so it would last
2. Was thick enough it would actually protect my car in both the summer and winter

Since I couldn't actually see it in person I used the product weight as a way to compare across product in addition to the description. The idea being given the same material, the heavier the cover the better the protection.

I'ved used it for several months now and am very happy I didn't try and save $10 to $20 and buy something cheaper. Specifically:

1. Fit -- It fits my car just the way it said it would and the elastic around the edges feels very thick so it will last. To be clear, it doesn't fit like a glove where the mirrors have their own place to stick into but rather more like a mitten where all the corners and curves of the cover generally match the car itself well.
2. Durability -- This feels really well made and even if it is hot out when I take it off the car the car itself feels cool when I get in. A big plus. I haven't had it in a big rainstorm yet but I did notice some wetness after some rain on the outside of the cover and none on the inside or on the car itself.
3. The Lock -- The lock it comes with (connects from the middle of one side of the cover when it is on, under the car, to the other side) is okay but would be really easy to defeat. I'm guessing the key benefit is to: a) keep the cover from fully flying off in a huge wind storm (it hasn't even lifted off a corner so far in 40 or so actual days of use) or if someone tried to just mess with it.
4. Ease of use -- it comes with an attached bag but I usually just roll the cover up from the back of the car to the front with the bag attached but sticking out so it is easy to quickly put it on the car since I know I'm starting from the right end and with the right side out. When I've rolled it I just fold it over onto itself and put it in the trunk. Easy on, easy off.

Note, it doesn't have one of those windows for your license plate but if you need that where you park it would seem easy enough to simply magic market the license number on as I've seen others do.

Hope this helps. Lots of options out there. This met all my expectations and has worked really well so far. Well worth the price and pays for itself in reduced need for car washes and, I'm assuming, over the long-term a nicer car interior due to less UV and heat damange.