Silicone vs. FKM: The Real Difference Between These Two Rubbers
The short version: FKM (fluoroelastomer) and silicone are two very different rubbers. Silicone is soft and cheap, but it gets sticky, attracts dust, and eventually starts to smell. FKM - the material behind high-end dive straps and Rolex's Oysterflex - is denser, stays dust-free, never holds odors, and lasts for years. For daily wear, FKM wins hands down.
Table of Contents
- What is FKM?
- Silicone vs. FKM: a point-by-point comparison
- Is FKM dangerous? The PFAS question
- Does silicone have any advantages?
- How to tell a real FKM strap from a fake
- Why we chose FKM
- FAQ
What is FKM?
FKM is a fluoroelastomer, a high-performance synthetic rubber (its best-known trade name is Viton). You will find it on high-end dive straps and on Rolex's Oysterflex. In practical terms, it is a dense rubber that resists water, UV, chlorine, and chemicals without breaking down in the sun. It is not silicone, and you can feel the difference the moment you put it on.
Silicone vs. FKM: a point-by-point comparison
Feel and comfort
Silicone is soft right out of the box, but it sticks to the skin and picks up dust and hair. The watch community agrees across the board: silicone attracts dust and hair, FKM does not. FKM feels firmer at first, then molds to your wrist within a few days. Once broken in, you forget it is there.
Durability and aging
This is where the gap is biggest. Low-grade silicone yellows, warps, and cracks within a few months. A quality FKM strap holds up for five to ten years of daily wear with no visible wear.
Odor and hygiene
Silicone is porous: it soaks up sweat and eventually starts to smell. FKM has a non-porous surface, so it cleans up with a quick rinse and stays odorless. If you sweat or work out, that difference shows up every single day.
Resistance
Seawater, pool chlorine, sunscreen, UV: FKM handles all of it without flinching. Silicone wears down faster against the same conditions.
| Criterion | Low-grade silicone | FKM rubber |
|---|---|---|
| Feel | soft, slightly tacky | dense, firm, then molds to the wrist |
| Dust and hair | dust magnet | stays clean |
| Odor after wear | traps sweat | non-porous, odorless |
| UV and chlorine resistance | yellows, degrades | resistant |
| Lifespan | 6 to 24 months | 5 to 10 years |
| Break-in time | none | a few days |
| Hypoallergenic | varies | yes |
| Price | low | higher, but justified |
Is FKM dangerous? The PFAS question
Fair question, and one that comes up a lot. FKM is a fluoropolymer, so it technically belongs to the PFAS family. But it falls into the "low-concern" PFAS category - stable and solid - and contact happens through the skin, not through ingestion. As one watch enthusiast put it: "Your watch strap is probably the least concerning source of PFAS in your life." To date, no study has shown a proven risk from wearing an FKM strap normally. And silicone is not free of additives, either.
Does silicone have any advantages?
Yes, in fairness it does. Silicone costs less, it is soft right away, and you can find it everywhere. For occasional wear or a tight budget, it gets the job done just fine. But for daily use on a watch you care about, FKM is the better choice when it comes to longevity, long-term comfort, and hygiene.
How to tell a real FKM strap from a fake
Heads up: many straps sold as "FKM" on AliExpress or Temu are actually silicone. One buyer summed it up: "I have tried FKM straps from AliExpress - a lot of them are just silicone." Three simple tests:
- Feel: FKM is dense and firm; silicone is soft and slightly tacky.
- Dust: set it on a surface. Silicone will be covered in lint within minutes; FKM stays clean.
- Weight: at the same size, FKM is heavier and feels more substantial in hand.
For more on counterfeits and AI-generated renders, read our article on fake vs. real on AliExpress and Temu.
Why we chose FKM
At Maison Brassel, every one of our straps is made from FKM rubber - never silicone. It is a deliberate choice driven by durability, comfort, and hygiene, for pieces built to be worn every day. That is also why our Royal Pop AP x Swatch straps are FKM. Check them out in the Lepine collection and the Savonnette collection.
FAQ
Is FKM hypoallergenic?
Yes. FKM is inert, non-porous, and free of common allergens like the nickel found in metal buckles. It works well for sensitive skin, as long as you rinse it regularly like you would any strap.
How long does an FKM strap last?
With reasonable care, a quality FKM strap lasts five to ten years of daily wear without yellowing or cracking. Low-grade silicone often gives out in under two years.
Does FKM attract dust?
No, and that is one of its biggest advantages over silicone. Its non-porous surface does not pick up dust, lint, or pet hair. It stays clean far longer.
Can you swim with an FKM strap?
Yes. FKM is waterproof and handles seawater just as well as chlorine. Rinse it with fresh water after swimming to wash off salt or chlorine, and it will stay like new.
Does FKM smell after sweating?
No, unlike silicone. Its non-porous surface does not trap sweat or bacteria. A quick rinse is all it takes to keep it odorless, even after a tough workout.
What is the difference between FKM and Viton?
Essentially none: Viton is simply the best-known brand name for FKM (fluoroelastomer). A Viton strap and an FKM strap refer to the same family of rubber.
Silicone or FKM: the bottom line
Silicone gets you by; FKM lasts. If you wear your watch every day, FKM rubber delivers better long-term comfort, far better durability, and zero odor issues. It is, without question, the rubber to pick for a watch strap.
Photos: Maison Brassel.
Want the full picture? Read the complete guide to wearing your Royal Pop on the wrist.
