Outlier Supermarine Summer Storm Cap

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Manufacturer Description

Our Supermarine Cotton fabric is the absolute best combination of high water resistance and maximum breathability we’ve ever encountered, perfect for rainy day use. We made this version unlined so that it wears lighter from our classic cap form. We took out the lining and fine finished the insides with a waterproof Italian seam binding tape. Lightweight with a great combination of water resistance, breathability and UV protection for serious head coverage.


  • The Supermarine Cap
  • 100% Cotton woven in Switzerland
  • Highly water resistant and super breathable
  • Very wind resistant
  • Helmet compatible
  • Spot clean or have dry cleaned
  • Made in New York City in collaboration with master milliner, Victor Osborne
  • Available in 3 sizes (head size)
    • Small – (21.5 – 22 in)
    • Medium – (22.5 – 23.5 in)
    • Large – (23.5 – 24.5 in)
  • Available in 3 colors – Anthracite Gray, Navy, Black
  • Measured weight – 50 g (1.8 oz)
  • Retail – $75

YMMV Review

Up until a while ago I had never heard of Outlier. Then one day I was reading and article about the top cycling caps, and this was one of the ones listed. I decided to take a look at the different caps online and opted for a different cap on price. Fast forward ahead a year or so and Outlier came across my path again and this time, I reached out to see if I could do a review of this superior cycling cap.

Front View

Outlier makes high end clothing with the idea to perform better every day. They are made using fashion driven design process and high quality technical fabrics. Their clothing has tailored quality which I like. Most of all, they make clothing that can be used across a variety of activities throughout your day.


The Submarine Cycling Cap is made for inclement weather, but I tested it in all types. We have had a slow starting summer, so I had a couple of rides in the weather where I wore this under my helmet. I also donned the cap a couple of days just to the office and around town.

Design ★★★★½

Appearance (25%) ★★★½☆

Construction (40%) ★★★★★

Materials (25%) ★★★★★

Sustainability (10%) ★★★★☆

What makes the Outlier Supermarine Summer Storm Cap stand out are two things: the construction and the fabrics. The Storm Cap is made in New York City. They are made in collaboration with the master milliner, Victor Osborne. The cap is made of several panels and pieces of fabric that have been joined with tight stitching and waterproof Italian seam binding tape. The cap is unlined unlike its Winter cousin which has a lining for warmth. What really set this apart is the fabric. It is a Supermarine Cotton that can best be described by Outlier themselves. This has been taken from their website:

Back View

The secret to the future, they say, is hidden in the past. Supermarine® Cotton is a 21st century edit to a nearly forgotten World War II fabric. You can think of it as the pinnacle of cotton technology, extremely breathable, highly water resistant and completely windproof. It can only be made using the longest staple Egyptian cotton fibers. They are woven together in a complex weave that swells up and seals when exposed to water. The result is a beautiful cloth that we think is the best rainy day fabric around.

For decades it’s been obscured from the public, kept alive mainly by demand from a few Air Force units, Antarctic explorers and funnily enough, bird watchers; all who have different understandings of its unique properties. Supermarine® Cotton stays comfortable under pressure and there is none of that sweaty/clammy feeling you get with GoreTex and other synthetic “waterproof-breathable” fabrics. It isn’t technically “waterproof” by government standards but you can stay dry for hours in the rain wearing it. It’s woven from the longest staple Egyptian cotton so it breaks in beautifully. The dense weave combined with the premium fiber results in a fabric that is simultaneously tough and supple.

Historically this fabric is an updated version of a fabric the British invented in World War II to keep their pilots alive in the North Sea if they happened to get shot down. It was later used by the British Navy, in Antarctic exploration and by Edmond Hillary during the first ascent of Mount Everest. It was even used to make firehoses and eventually found its way into high-end hiking gear. Since it requires a very dense weave of the most expensive cotton fibers on the market, it never quite broke through into the mainstream and with the advent of GoreTex it faded from the general marketplace. Bird watchers still sought it out since it’s significantly quieter than the loud synthetic fabrics that took over, while Antarctic teams prized it for its amazing windproof quality. The main customer of the past few decades however has been various Air Forces who understood just how superior a fabric it is, and are willing to pay for it. 

Side View

We source our Supermarine® Cotton from Switzerland (where it goes by the tradename ETAProof®) and it differs from the historical British version in one important respect, it is treated with a premium durable water resistance (DWR) that is not wax-based. The water resistance in the historical formulation comes from two factors, the denseness of the weave and the fact that cotton fibers swell up when exposed to moisture. Adding the DWR treatment into the mix results in a significantly superior rain repellant and breathable fabric that far outclasses both the synthetic “waterproof-breathable” fabrics of the world and the heavy, clammy Barbour-style waxed cotton. It looks better, wears better and is dramatically more comfortable.

We’ve been testing this stuff extensively over the past year and we keep on thinking we’ve stumbled upon a little bit of magic. We made button down shirts and walked out into torrential downpours without a jacket or umbrella. We’ve done hours of laps in Prospect Park during thundershowers wearing the same shirt and stayed dry. We’ve taken it out into 100% desert heat to see how well it breathes. We challenged our bike messenger friends to beat it up on the road. More important than all that though was the fact when we headed out of the house, we almost always reach for a Supermarine® Cotton shirt or parka, not because we wanted to test it, but because we wanted to wear it.

It is almost poetic in the way they describe the fabric and for that reason I wanted to include their description as I could not do it justice. The fabric is not entirely waterproof but is highly water resistant. The current test for waterproofness stacks a column of water on the fabric and sees how much water can be stacked before it penetrates the fabric. Due to the nature of this fabric it will not stand up to that test but will effectively keep you dry in everything except a fire hose. The fabric is also very wind resistant and breathable.

The cap has a stiff bill at the front to protect the eyes and keep rain off the face. Inside the cap, there is a fabric headband for comfort and an elastic back to hug your head and stretch to fit. There are three available sizes depending on your head size. It comes in three colors: navy, gray anthracite, and black. It is helmet compatible but looks good on its own as well. If you do need to clean the cap, it will need to be dry cleaned.

Victor Osborne Label

Outlier is a smaller company and as so does not have all the resources to create sustainability initiatives like the larger ones do. They do make their products in the US with fabrics that are for the most part, renewable. They are one of those brands that are doing it right, and I hope they can continue to do so.

Fit ★★★★☆

Bill (25%) ★★★★★

Comfort Next to Skin (25%) ★★★★☆

Head Sizing (50%) ★★★½☆

The Supermarine Summer Storm Cap comes in three sizes based on your head measurements. I opted for the size medium and can comfortably say that their sizing chart is accurate. I fell in the middle of the size range, and I feel like I am in the middle of the fit on this hat, which is about perfect. The back of the hat has an elastic stretch to it so it can accommodate a range of sizes while still feeling snug on the head. With all the panels used to make the cap it contours to the shape of my head well. The does appear to be a couple (4) pointy spots on the head, and I am hoping those will go away slightly as the hat breaks in. They do not look bad by any way but are the couple locations that are not snug to my head.

Next to the skin is a fabric headband which is comfortable and soft. It also helps wick moisture away if you do happen to break a sweat. On the inside of the hat all the seams are finished and lay flat so you do not feel them against your skin. When wearing this hat with or without a helmet, it was equally comfortable. My favorite part of the cap is the small bill. It is stiff so it maintains shape and does not droop into your eyes. It is also just the right size to add coverage but not block your vision. I have several other cycling caps that I wish had bills as nice as this one.

Top View

Performance ★★★★☆

Breathability (35%) ★★★½☆

Durability (30%) ★★★★½

Weather Resistance (35%) ★★★★½

The Supermarine fabric is quite impressive. It looks like cotton yet is essentially waterproof. It kept me dry in some light rain here in Bend and for a more thorough test, I played around with it on in the shower and was pleasantly surprised. The cap does breathe well, but it is possible to overwhelm t like any other cap on hot enough days. When I did this, the fabric headband soaked up the sweat well and did not feel wet to my skin. It did take a little longer to dry than other fabrics often take, the headband that is. I have not had the cap long enough to see if it will break in more like claimed, I am sure it will, but right now it still looks like new. I am sure if it is a good enough fabric for the Armed Forces it will be durable enough to use as a cycling cap. If anything does arise, I will check back in here. It does feel extremely well made, you can tell it is top notch. While it does breathe, I would classify it as just enough to let out heat but not enough to feel the air coming through. On my rides, I was not able to feel any wind getting through the fabric; it is essential windproof or highly wind resistant. As for water, I addressed it above; it beads up and runs off the cap. The DWR works and in my testing, no water was able to soak through.

Tight Seams Inside

Overall ★★★★½

Overall, the Outlier Supermarine Summer Storm Cap is a really nice cycling cap. The fit is well done, and the construction is obviously very high quality. I was also impressed by the performance of the fabric. Outlier definitely romanticizes the fabric, and I was a bit skeptical about all the hype. I can say it was a very solid fabric with great qualities. I would be intrigued to see how well it would work in other pieces of clothing that have more demanding roles. As a company, I like how they are making products with clean lines, great fit, high-quality materials, and versatile usage. I think this is great for people who want high quality long lasting gear and do not want to have everything under the sun. Now is it worth the retail price of $70? It is expensive, but you get a well-made and high-quality cap. I think I would say that it depends on how often you will use it. If it will not be worn much than probably not, but if you wear your caps quite often, then I would recommend it. As always, your mileage may vary.


  • Great looks
  • Breathable
  • Water resistant
  • Very well made
  • Front bill is a perfect size
  • Made in New York


  • Expensive
  • On me there are four pointy spots from the design

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About the Author

I am an avid runner, cyclist, swimmer, hiker, climber, skier and many other activities that would make this list too long. I started Your Mileage May Vary Reviews in Early 2011 to combine two of my passions: sports and gear.

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