Armin Strom · Gravity

Strap for Gravity Fire

Takes 20 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width20 mm
Case diameter43 mm
ReferenceRG13-GF.90
FamilyGravity
MovementArmin Strom caliber AMR13 Hours, Minutes, Small Seconds
CaseRose Gold

Spring bar

Swiss Standard universal spring bars

The right category for this model · 316L steel, all lug widths 13–26 mm

Straps for the Gravity RG13-GF.90

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The Gravity RG13-GF.90, seen from the bench

The Armin Strom Gravity reference RG13-GF.90 is equipped with the in-house manufactured caliber AMR13 with hours, minutes, and small seconds indication. The movement features a gravity-driven architectural design with visible components on the dial. The case houses the automatic caliber developed internally by the Swiss maison.

Frequently asked questions

What is the lug width of the Armin Strom Gravity RG13-GF.90?

The Armin Strom Gravity RG13-GF.90 features a lug width of 20 mm, a standard measurement for many excellence-grade sports watches and dress chronographs. The lug width is measured as the distance between the two terminal ends of the case lugs, where the strap attaches. For the RG13-GF.90, this measurement is precisely 20 mm, ensuring absolute compatibility with certified straps of this width.

Which strap material is recommended for the rose gold Gravity RG13-GF.90?

To enhance the rose gold Gravity, we recommend an alligator strap with vegetable tanning (dark brown, mahogany, or burgundy tones) or a shell cordovan strap, which develops a noble patina over time. Alternatively, a smooth calf leather of generous thickness (1.4–1.6 mm) provides contemporary elegance. For intensive daily use, FKM rubber with high modulus properties protects the case while preserving its finish.

How do I change the strap on the Gravity RG13-GF.90?

The Gravity RG13-GF.90 strap is replaced using the spring bar release mechanism at both case lugs. Using a spring bar tool, gently push the pin inward and lift the strap away from the lug terminal. Repeat on both sides. To install the new 20 mm strap, align the holes with the spring bars and lower carefully until you hear the click of engagement. Avoid sharp impacts to protect the case finish.

Can I use an aftermarket strap on the Gravity RG13-GF.90?

Yes, absolutely. The Gravity RG13-GF.90 is fully compatible with quality aftermarket straps, provided they are certified for 20 mm lug width. Specialised craftsmen brands such as Milano Straps offer straps in alligator, calf leather, shell cordovan, and technical textiles, all engineered for this standard. Mechanical compatibility is assured; simply verify the lug width (20 mm) before purchase.

How long does a leather strap last on the Gravity RG13-GF.90?

Longevity depends on material and usage patterns. A quality handcrafted alligator or calf leather strap, worn daily, develops nobly for 5–7 years before requiring replacement. Shell cordovan resists longer (7–10 years or more), continuously improving with natural ageing. Wear manifests gradually: leather softens, develops patina, and edges round naturally. To extend lifespan, avoid prolonged direct humidity exposure and protect the strap from intense heat sources.

The next step

The right strap isn't chosen. It is built, together.

From the atelier appointment to delivery, every step is made for those who know that things done well take time. Rare leathers, one piece at a time, eighteen months of warranty.

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Casati Milano · Via XX Settembre 15, Milan · by appointment only