Ask PM | Winter Fabric: Flannel, Covert and Super Wool

To some, it’s just fabric. To us, fabrics are a plethora of possibilities. Flannel, covert, super worsted—all 100% wool but all very different in terms of weave, texture, functionality, and drape. So, what is the difference, and what would be a good choice?


When colder weather arrives, I really look forward to wearing my flannel suits. It’s amazingly warm, supremely soft, and darn cozy. I don’t mind keeping it on when I get home in the evening and pouring a glass of wine and relaxing before getting into my homeware—it’s just comfortable. 

Flannel usually ranges from around 280 grams all the way up to 450+ grams. I prefer something around 340-380 grams—not only will it be warm for those colder days but it will also be hard-wearing. Not to mention, when it’s a bit heavier, the trouser’s crease will keep longer and wrinkles will just drape out, making it easy to take care of.

However, if you find that you are always cold, simply go with a heavy flannel of 400+ grams or if you live in an area that has more mild winters, you might prefer a lighter flannel around 300 grams.

PM by Principle M Grey Flannel Suit
Using Italian 340g Flannel

A mid-grey flannel suit is extremely elegant, classic and super easy to wear. If you don’t have a flannel suit, I’d recommend going with grey since you can also easily break it up. 

Flannel is a bit muted due to the brushed nap surface, so if you are looking to have a bit more expression, go with slightly bolder colours since it will be a bit subdued.


Are you the kind of person that rarely wears your new sneakers because you are worried they will get dirty or scuffed up? If so, Covert wool is a great option for you. It is possibly one of the most durable wool fabrics there is.

It is a steeply woven twill cloth made from tightly spun yarn making it very dense, which makes it durable as well as wind and water-resistant. In the fall and winter, the elements tend to be a bit rougher—strong winds, cold rain or even snow—which makes covert a fantastic option and suitable for the weather. 

Covert tends to be in the neighbourhood of 400 grams or more, making it a heavy fabric. The finish of the fabric has a very smooth hand and sometimes a natural sheen—I like the contrast with a flannel or tweed jacket.

Although covert has been historically more popular for coats or trousers, they make a very interesting full suit and we’ve done more of this in recent years. Since it is a heavier weight, the drape will be very clean and crease-resistant. Not to mention the density will make it extremely durable, so you won’t have to worry about snagging the fabric if you accidentally brush up against something. The flip side of such a dense and durable fabric is that it has little to no natural elasticity, so if the suit is slightly tight or there isn’t enough drape in the back for movement or through the hips and legs, it could be a bit uncomfortable to wear all day long. However, if the cut and fit are right, that shouldn’t be a problem. 

B&Tailor Bespoke
Caccioppoli Charcoal Suit

Since covert is a twill and can have a bit of a natural sheen, it can make a very nice formal suit. My charcoal 3-piece covert is one of my go-to suits if I want to have a more formal outfit. The colour range is a bit traditional in coverts but something in a beige, brown or olive can also be very charming and a bit less formal than a charcoal suit and easy to break up. 

Super Wool

As technology in weaving has become more advanced, they have been able to weave finer fabrics, such as super 150’s and above. These fabrics will be finer, softer and more supple, which can make for a very comfortable and luxurious suit.

Many people believe that super fabrics are better. Some may perceive it to be better because the number increases —120’s, 150’s 170’s and beyond—or because the word ‘super’ is attached to it. We should first take a look at what super fabrics are.

Scabal ‘Jet Set’ 

There are several factors that could be considered in what make a super fabric: the diameter of the fibers, breed of the sheep, average length of the fiber and crimp to name a few.

Two of the most important and measurable factors are the average diameter and length of the fibers. The diameter is measured in microns (1 micron = 0.001mm), for example the average micron of a super 150’s is 15.76-16.25 microns or super 200’s 13.26-13.75 microns.

Hard to imagine how thin that is? Here is a diagram that shows a human hair, white blood cell and super 150’s fiber diameter in proportion.

The thinner a fiber is, the harder it is to spin it into yarn, especially if the fibers are short. So, if the length of the fibers is longer they can be spun into yarn more easily, which can then be woven into fabrics. The super thin and long fibers are simply less in supply and make a very fine fabric, which is why super fabrics are rare and luxurious

Super fabrics make for a very sleek, elegant and sharp suit. The weight of super fabrics tends to be around 270g, making it a decent four-season suit that you can enjoy year-round. The fineness of the fabric makes them extremely comfortable, the issue is that they will not be very crease resistant nor hard wearing. Also, because of the soft fabric, the drape may not be as crisp or wrinkle-resistant as other fabrics.

I like putting on my super 150’s Scabal three-piece suit for special occasions or important meetings. I know that this wool is rare and the feel is quite luxurious, but it isn’t a suit I wear multiple times a week. So, when I do wear it, I do feel it is a little treat.

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