Articles

Over 3 Million "4S Shirts" Sold by Suit Select: The Japanese Technology Behind "Non-Iron" Clothing

2025.05.27

In today’s business wear, comfort is a must-have feature.

And comfort isn’t just about how clothing feels—easy care matters, too. Take, for example, no-iron shirts that require zero ironing.

In this fiercely competitive market, where major suit brands are constantly vying for the top spot, Suit Select’s 4S Shirt stands out for its exceptional quality.

First launched in 2017, the 4S Shirt has now surpassed a cumulative total of 3 million units sold. But what truly sets it apart from competitors? We interviewed the product manager involved in its development to find out everything.

PROFILE

Shota Ueno

KONAKA CO., LTD.
Merchandising Division Buyer, Deputy Manager

What Are the Four "S"s that Win the Hearts of Modern Businesspeople?

Can you start by telling us about the Suit Select brand?

Supervised by creative director Kashiwa Sato, Konaka Co., Ltd.’s suit brand.

Currently, we have 180 stores across Japan, offering a wide variety of products—mainly suits, but also shirts, ties, and everything from formal to casual wear.

"4S Wide Collar Dress Shirt," 4,290 yen (tax included)

What kind of shirt is the explosively popular 4S Shirt?

It’s a business shirt that debuted in February 2017.

The name "4S" comes from four key features: SUPER NON-IRON, STRETCH, SOFT TOUCH, and SLIM—each a functionality represented by an S.

Outstanding Wrinkle Resistance that Meets JIS Standards

The first S stands for "Super Non-Iron"—is there high demand for no-iron features?

The demand for easy-care business wear is only growing.

We often hear customers say, "Ironing is a hassle" or "It’s tough to get to the cleaners." The appeal of a no-iron shirt that can be simply washed at home is obvious—it fits a world where time performance is valued more than ever before.

So what distinguishes the 4S Shirt from standard no-iron shirts?

These days, many brands use the terms "no-iron" or "non-iron," but there’s actually no strict definition for either.

However, there is a standard for wrinkle resistance—Japan’s JIS standard for "W&W performance (Wash & Wear)." If a shirt scores 3.2 or higher on this scale after being laundered, it qualifies as a wrinkle-resistant or no-iron shirt.

The 4S Shirt scores at least 4.0 for W&W performance, earning it the title of "Super Non-Iron."

Compare a regular shirt after washing (left) and a 4S Shirt (right)—you can clearly see how the 4S Shirt stays almost wrinkle-free.

This wrinkle-resistant advantage isn’t just for everyday use—it really shines on business trips or during long journeys.

Superb shape retention, indeed.

The maximum W&W performance is 5.0 (fully non-iron), but as the score goes up, so does the price.

On that point, the 4S Shirt is just 4,290 yen (tax included) per piece. There are almost no truly super non-iron shirts at this price point on the market. It's this exceptional cost performance that I believe explains why the 4S Shirt is so highly rated.

The secret behind its shape-retaining properties lies in its 100% polyester warp-knitted fabric.

What kind of material is used?

It’s a high-performance polyester that offers various functions such as quick-drying and stretchability. However, the outstanding shape retention of the 4S Shirt also owes much to the way it’s knitted.

In fact, this shirt isn’t made from woven fabric—it’s made from knit. There are three main knitting methods: weft knitting, warp knitting, and circular knitting. This shirt uses a warp-knit material known as “tricot.”

Tricot, despite being a knit, has the unique feature of retaining its shape like woven fabrics. It’s soft and supple to the touch, resists wrinkling, and is often used in sportswear and underwear.

As you’d expect from knit fabric, it also offers excellent stretch, expanding and contracting both vertically, horizontally, and diagonally. Compared to ordinary woven stretch fabrics, it provides about two to three times more elasticity.

A polyester knit—who would've thought? But it feels as soft as cotton fabric on the skin.

Not long ago, many shirts made with polyester for easy care felt stiff and weren’t really comfortable.

That's why, with the 4S Shirt, we focused on using high-performance polyester while also creating a texture that feels as close as possible to 100% cotton.

First, we chose polyester yarns with cross-sections as round as possible, like cotton. This creates a flexible, cotton-like touch.

Then, by knitting with ultra-fine yarn at a high gauge, we achieved even softer texture and improved quick-drying performance.

However, warp-knitting with ultra-fine polyester yarn is extremely difficult, and production is currently possible only at a knitting factory in Fukui Prefecture, Japan.

Fabric produced at a knitting factory in Fukui, Japan

An Original Material Born from Plenty of Trial & Error

How did you come up with this material?

The first shirt we ever made was a 100% cotton non-iron shirt. While it was well received, some customers were dissatisfied with how some wrinkles remained. So, we set out to develop a shirt that truly didn’t need ironing.

That was how it all began.

After that, we shifted to woven polyester fabric for better shape retention. However, this fabric was a bit stiff, and comfort was still an issue.

Next, we tried polyester knit material, but found flaws: you couldn’t iron it and, with continued wear, the fabric started stretching out.

That’s when we discovered the warp-knitted polyester knit made at a Fukui factory.

The result was a shirt with both satisfying shape retention and comfort. In February 2017, we launched the 4S Shirt. Thanks to that, we’ve earned strong support from many customers.

A Shirt Designed to Look Sharp—Even When Worn on Its Own

There must be reasons why it sells so well, besides its shape retention and comfort.

One reason for the 4S Shirt’s popularity, in my opinion, is the "SLIM" function it offers.

When creating this shirt, we placed great importance on making sure it would look sharp even when worn solo.

To make that happen, getting the silhouette right was crucial. We designed the patterns carefully so that the stomach and chest areas look sleek when worn.

What we focused on most was the area around the arms and shoulders. We narrowed the armholes slightly to reduce bagginess, but added ease at the shoulders for full range of motion.

The sleeves also taper from the upper arm towards the cuffs, similar to tapered pants, so the arms look sharply contoured.

It certainly makes your silhouette look sharp and polished.

Shirts used to be a supporting player, merely an inner layer beneath a suit, but that's no longer the case.

Especially during the spring and summer seasons, many businessmen commute wearing just a shirt without a tie, and the demand for "shirts that can take center stage" has grown.

There are now plenty of design variations, with wide collars and button-downs being especially popular, and colors like white and blue leading the trend.

"4S Button Down Shirt," 4,290 yen (tax included)

How will the shirts continue to evolve from here?

We plan to roll out the 4S Shirt lineup with even greater functionality in the future.

Currently, our oil guard shirts, which feature a special surface treatment that resists skin oils and stains, are especially well-received.

We've also introduced a cotton 4S Shirt as a derivative model for customers who value the natural texture and comfort of cotton.

"4S Cotton Dress Shirt," 6,490 yen (tax included)

A truly non-iron shirt that's exceptionally comfortable and cost-effective—plus, it looks stylish even on its own. This is the business shirt of your dreams.

The 4S Shirt will keep getting better, staying ahead of the times and meeting new demands as they arise.

Text by Ryota Osujo