21/23oz Ultra Heavy Raw Selvedge Denim Straight Cut Jeans IH-634S-UHR - Indigo

The Iron Heart IH-634S-UHR in 21/23oz Japanese selvedge denim in indigo is available at Rugged Gentlemen Shoppe with fast local shipping and easy returns. Iron Heart produces limited runs of each model, and popular sizes are often difficult to find. If your size is available, you can secure it here while stock lasts.

Our classic straight-cut jeans constructed from our 21/23oz UHR denim. UHR is an acronym for “Ultra Heavy Raw”, an unsanforised and loomstate fabric, UHR denim fabric starts at 21oz, and becomes (approximately) 23oz after shrinkage. The UHR enjoys virtually legendary status amongst aficionados and fans of the brand, due to its fading potential, and the density of the weave.

Our Fit Notes

The 634 is Iron Heart’s classic straight cut, offering a mid rise and an even fit through the leg. It provides more room than the 555 and 666, making it a reliable reference point for those new to the brand.

Our Fabric Notes

Iron Heart’s 21/23oz Ultra Heavy Raw (UHR) denim is one of the brand’s most demanding fabrics. Woven as an unsanforized, loomstate selvedge denim, it begins at 21oz in its raw state and becomes approximately 23oz after the first wash and shrink.
The fabric is extremely dense and rigid when new, requiring a significant break-in period. Initially, it can feel very stiff, but with consistent wear it softens and develops pronounced, high-contrast fading. Due to its unsanforized nature, the denim will shrink after washing, allowing the wearer to achieve a more personalised fit over time.

Who This Is For

Best suited for experienced raw denim wearers or those specifically looking for a true shrink-to-fit experience. This fabric appeals to enthusiasts who appreciate heavyweight denim and are willing to invest time into the break-in process for long-term character and durability. For those who prefer a traditional straight-leg fit and a balanced, all-around silhouette.

Made In Japan

• Designed by Shinichi Haraki, handmade by WORKS INC. in Japan

634 Straight Cut

• Traditional straight cut, inspired by the 1966 Levi’s 501
• Medium Rise
• Straight leg profile with a slight taper from knee to hem
• Wider leg opening to accommodate most types of boots and footwear
• Classic 5-pocket design

21/23oz Ultra Heavy Raw Japanese Selvedge Denim

• 100% cotton
• Woven with a double twisted weft yarn
• Indigo rope-dyed warp/ white weft
• Right-hand twill weave
• This denim will fade naturally through wear and washing

Hardware & Construction

• Traditional 3-button fly
• Iron Heart branded tack button at waistband
• Works Inc branded pocket rivets
• Hidden rivets on rear pockets
• Poly/cotton stitching for increased strength
• Single and double needle chain stitch construction
• Belt loops anchored at three points and sewn into the waistband
• Heavy cotton pocket bags and lined rear pockets

Selvedge ID

• Sideseam, fly, and coin pocket selvedge ID

Leather Patch

• Heavyweight vegetable-tanned steerhide
• Natural finish
• Belt-through design
• Debossed Iron Heart graphic
• Please note: Continued washing (especially at higher temperatures) may cause shrinkage and deformities

Technical Details (Iron Heart Specification)

• This is a raw, loomstate denim that has not been sanforized. Sanforization is a post-weave mechanical process that removes most potential shrinkage from a fabric before garment construction.
• As this fabric is unsanforized and unwashed, the garment will shrink after soaking or washing. The amount of shrinkage depends on washing conditions, but typically results in reduction across the waist, inseam and overall dimensions.
• Expect approximately 1" shrinkage in the waist and up to 2" shrinkage on the inseam after an initial soak or wash.
• Post-wash, areas under tension such as the waist will gradually stretch with wear.

Care Guidelines

• We recommend washing this garment at 30°C with a low (or no) spin cycle. Hang dry, do not tumble dry

Sizing & Shrinkage Notes (Our Advice)

• This model uses unsanforized (loomstate) denim, meaning it has not been pre-shrunk and will reduce in size after its first wash. Because of this, the jeans may feel larger when new but will settle into a closer fit once soaked or washed.
• In practice, most of the shrinkage occurs early, after which the denim will gradually adapt to your body through wear. Some customers choose to allow for this shrinkage when selecting their size, depending on how they prefer the jeans to fit after break-in.
• Unsanforized denim behaves differently from standard Iron Heart jeans. If you are used to sanforized models, sizing may require a different approach.
• If you are unsure, we are happy to advise based on the measurements of the pair we have in stock.
• Note: For best results, consider your preferred fit after shrinkage rather than the initial raw measurements.

Measurement in inches (before wash)

FAQs

Is this authentic Iron Heart?
Yes. All products sold by Rugged Gentlemen Shoppe are 100% authentic Iron Heart items sourced from Iron Heart Japan.

Why is this sold out elsewhere?
Iron Heart produces limited quantities and popular sizes sell out quickly on the official site and major retailers.

How fast do you ship?
Orders ship from our shop within 24–48 hours (business days).

Can you help with sizing?
Yes, contact us before ordering and we’ll provide real measurements for the exact pair in stock.