IRON HEART（アイアンハート） is a Japanese clothing brand with roots in motorcycling and heavyweight denim. One of its defining pairs is the 634S, a straight-cut jean made from 21oz indigo selvedge denim. It offers a different starting point from a graphic pocket design or a vintage reproduction: substantial fabric built around an everyday, wearable cut.
This guide introduces the brand through that model, explains what to check before choosing heavy denim, and separates the Japanese-store price from the international buying route.
IRON HEART at a glance
| Brand | IRON HEART（アイアンハート） |
|---|---|
| Founder | Shinichi Haraki（原木真一） |
| Established | 2002, according to the official brand history |
| Background | Clothing developed with the Japanese motorcycling community in mind |
| Model in this guide | 634S / IH-634S, indigo |
| Fabric | 21oz selvedge denim, 100% cotton |
| Manufacturing country | Japan, as stated on the product listings |
From garment-making experience to motorcycle clothing
The official international history dates the brand and Works Inc. to 2002. Founder Shinichi Haraki had spent around 20 years in Japan’s clothing industry, beginning as a pattern maker at Edwin. He brought that experience together with his interest in motorcycles to develop a brand focused on heavyweight denim and durable fabrics.
The same history dates its international partnership with Giles Padmore to 2005. That helps explain the two official shopping routes a reader may encounter: the Japanese store and the UK-based international operation.
The Japanese 634S introduction dates the model’s launch to 2003. The brand’s establishment and a particular model’s release are separate milestones.
Meet the 634S: a heavyweight straight cut
The international IH-634S listing describes a medium-rise straight cut, with a slight taper below the knee and a leg opening intended to accommodate boots. Its signature 21oz denim combines indigo warp yarns with a white weft, using a double-twisted weft yarn and a lower-tension weave.
Iron Heart describes the result as substantial yet supple for heavyweight denim. That is the manufacturer’s description, rather than a hands-on comfort assessment for this guide.
- Cut: straight, medium rise
- Fabric: 21oz, 100% cotton
- Fastening: button fly
- Origin: made in Japan
- Finish: the international listing specifies sanforized and one-washed; the Japanese listing also states one-washed
What does 21oz mean for choosing jeans?
The weight figure describes the denim fabric, not the total weight of the finished pair. It gives you one useful comparison point, but it cannot tell you everything about texture, flexibility or fit.
Before buying, think about where the jeans will be worn. Consider the weather, how long you sit, the footwear you use and whether you enjoy a substantial fabric. If you have only worn light stretch jeans, trying this kind of denim in person is particularly useful.
Do not choose a tighter size simply because you expect the waist to stretch. Start with the seller’s current measurements and check the thigh, rise and leg opening as carefully as the waist. Comfortable movement matters from the start.
Japan price and the international buying route
The official Japanese 634S indigo listing showed ¥34,100 including tax (¥31,000 before tax) when checked on November 6, 2026. Treat this as a listed price, not a promise that your size is available.
The Japanese store explicitly states that it does not ship internationally and directs overseas shipping orders to Iron Heart International. It also excludes forwarding and proxy purchasing services. Overseas readers should use the international store or ask an authorized stockist about availability and the applicable final price.
634S at the official Japanese store →
IH-634S at the official international store →
Washing and getting the length right
The international IH-634S guidance recommends washing at 30°C with a low or no-spin cycle, then hang drying rather than tumble drying. It describes the sanforized, one-washed fabric as having little remaining shrinkage under the recommended care conditions. Follow the instructions for your exact pair.
Before hemming, decide how the jeans should sit with your usual shoes and whether you want a cuff. Ask the seller about its measuring method, alterations and return conditions before placing an order.
Explore other approaches to Japanese denim
For more context, compare this guide with our articles on MOMOTARO JEANS（桃太郎ジーンズ）, STUDIO D’ARTISAN（ステュディオ・ダ・ルチザン） and EVISU（エヴィス）. Each offers a different combination of fabric, cut and visual identity.
Sources
- Iron Heart — official brand history
- Iron Heart International — IH-634S specifications, finish and care
- Iron Heart Japan — 634S, Japanese price, manufacturing origin and shipping conditions
Official information checked November 6, 2026. This is a researched brand guide, not a hands-on wear test. Illustrations do not depict actual branded products.
