Replacement FKM Rubber Strap for Cartier Santos WSSA0009/WSSA0018 – QuickSwitch System

Product Overview

The Cartier Santos de Cartier Large is a 39.8 mm square-cased watch with a quick-release system hidden inside the lugs, and this strap is moulded to meet it. Instead of trimming a universal band to size, the ends are shaped from the case profile, so the strap sits flush against the watch with none of the lifted edge or shadow line a straight-end band leaves behind.

The material is FKM fluororubber — a fluoroelastomer that resists sweat, sunscreen, oils and UV instead of softening or going tacky the way cheaper rubber can. It has a smooth matte finish, which makes it read as a quiet, sporty alternative to the original steel bracelet or leather band rather than a glossy accessory.

Like the other custom fluororubber material watch straps in this range, this one is cut for a single case. That is the point: the Santos Large keeps its square case and Roman dial, but the watch becomes lighter on the wrist and comfortable through a hot commute, a workout or a walk in the rain.

Fitting it needs no tools. Quick-release spring bars come already seated in both ends and the ends themselves are rubber, so there is no metal edge pressing against the polished case while you work. The watch shown in the photographs is for display only and is not included.

Santos Large Reference Fit

• Made for the 39.8 mm Large case. Both references named at the top of this product share the same square case, the same lug opening and the same hidden quick-release system, so one strap shape covers either watch.
• Check the case back first. The reference is engraved there. If it matches, the strap seats straight into place; if the engraving is worn or hard to read, send us a photo and we will identify the case for you.
• Measure the opening, not the old band. The most common mistake when buying a watch strap online is measuring the bracelet at its widest point. Measure between the lugs, across the spring-bar opening, and compare that figure with 21 mm.
• Two widths at the two ends. The case end carries the full Santos Large width; the clasp end narrows so it will pass through an 18 mm folding clasp. Both figures matter when you choose a size option.
• Moulded ends close the gap. The end profile follows the case curve, so there is no daylight between strap and case — the detail that separates these custom fluororubber material watch straps from a plain flat band of the same width.
• Large case only. This pattern is shaped for the 39.8 mm Large. If you own the smaller Santos case, use the strap made for that case rather than forcing this one onto it.
• A replacement part, not a Cartier product. The strap is made by Fuerman as an aftermarket alternative, and no Cartier branding appears on it.

Material & Build

FKM — fluoroelastomer — is the rubber used where ordinary rubber gives up. It holds its shape through heat, sweat, oils and UV rather than hardening, cracking or turning shiny, and its matte surface wipes clean instead of holding onto sunscreen and skin oil. Natural rubber goes stiff and pale with age, while silicone is softer but picks up lint and stretches. This custom fluororubber material watch strap keeps its matte finish rather than going glossy the way cheaper rubber does.

At 1.7 mm thick it sits low against the wrist. There is no padding under the case, so the watch keeps its flat profile and slides under a shirt cuff, and the underside is smooth against the skin rather than grippy.

Day to day that means one strap for the office, the gym and the sea. Salt water, chlorine, sweat and rain are all part of normal use for FKM. Rinse the strap in fresh water afterwards, dry it with a soft cloth, and let it air away from direct sun and radiators instead of folding it tightly into a drawer.

Keep sunscreen, insect repellent, solvents and heavy oils off the rubber where you can — those are the substances that dull any elastomer over time. Before each season, glance at the quick-release ends: they should sit tight in the case with no sideways play, and the spring bars should be straight rather than bent.

Nothing here needs conditioning, oiling or breaking in. The strap will not soften into shape the way leather does, and it does not need to come off the watch to last. It simply keeps doing what it did on the first day.

Specifications

QuickSwitch Fitting

1. Set up on a table, not on your lap. Lay a soft cloth down and work over it — the strap ends are small and a dropped watch on a hard floor costs far more than the strap.
2. Check the new strap before you touch the watch. Both spring-bar ends should sit level with the moulded end and should not shift sideways when you press them.
3. Release the old strap. Press the quick-release point at the lug and slide the strap out, then do the same on the other side and set the bracelet or old band aside.
4. Line the new end up square with the lug opening. Keep the strap level with the case rather than angled, so the moulded end seats the way it was shaped to.
5. Press it home until it settles. You should feel it stop with no gap at the case and no rocking when you move the strap by hand.
6. Repeat on the other side and test both ends. Give each one a firm but gentle tug and check the fit from the side; the end should follow the case curve with no daylight showing.
7. Refit your folding clasp and re-check after a day. Feed the tapered end through your original clasp, reuse the same pin or spring bar, then wear the watch for a day and confirm both ends are still flush.

Clasp Compatibility

• Built around your original clasp. The strap is designed to work with the 18 mm Cartier folding clasp that came with the watch, so the hardware you already own stays on the watch and nothing has to be bought twice.
• The tapered end is the reason it works. These custom fluororubber material watch straps narrow toward the clasp end rather than running straight, which lets an 18 mm folding clasp sit properly instead of pinching the rubber.
• Strap only, or complete set. Strap-only versions are listed for owners who already have the original clasp. Buckle-included versions are there for anyone who bought the watch on a bracelet without a clasp to reuse, or who wants a spare set ready.
• Your clasp keeps its adjustment. Nothing about the strap changes the length setting you have already dialled in, so the watch goes back on the wrist exactly the way it came off.
• Different clasp style? Say so. If your watch is fitted with something other than the standard folding clasp, tell us the style and the width across the pin fitting and we will confirm whether the tapered end suits it before you choose a size.
• Keep the small parts together. While you swap straps, put the clasp pin or spring bar and any spare part you remove somewhere you will find them again — the pin is the one piece that is easy to lose and awkward to replace mid-job.

Colour & Finish Options

Ordering & Fit Confirmation

1. Confirm the watch. Note the reference on the case back, or measure the opening between the lugs, before you choose anything else.
2. Decide whether you need the clasp. Strap-only versions are for owners reusing the original folding clasp; buckle-included versions suit anyone starting without one.
3. Choose the size option that matches both ends. The case end and the clasp end are different widths, and the listing carries both figures.
4. Pick the colour, and ask for a photograph if the exact shade matters. Natural light shows rubber colour more honestly than a phone screen.
5. Check the length against your wrist. If you are between sizes, send your wrist measurement and we will tell you what to expect before you order.
6. Ordering a watch strap online is straightforward once the reference is settled: message us with the case reference and your clasp style, and confirm stock, delivery timing, shipping and return terms for your order before you pay.
7. Keep the original parts safe. Store the bracelet or old strap you removed together with its pins and links, so the watch can always be returned to its original state.

Technical Support & Model Matching

FUERMAN has been supplying watch parts and accessories from Huadu District, Guangzhou since 2010 — 15+ years in the trade, a 60-strong team and a deep ready stock held in China. Our technical team, which includes technicians with 30+ years of watchmaking experience, matches items to your watch by brand, model or reference number before you order, so you know it will fit. Send a photo or a measurement if you are unsure: we will confirm the right choice, talk you through fitting, and stay with you afterwards — troubleshooting, replacement parts and after-sales help long after your order arrives.

FAQ