Choosing the right convertible top fabric isn’t just about color or texture — it directly impacts durability, weather resistance, sound insulation, and how well the top functions over time.
In most shops, three Haartz-made materials dominate the market: Sonnenland A5, Twillfast RPC, and Stayfast. Each has its place, but they perform differently when it comes to installation and long-term use. Here’s a rundown from OEM+ Auto Tops on how they compare.
Sonnenland A5 ($$$)
Made by: Haartz, Germany
Build: Three-ply — acrylic twill weave outer, rubber core, polyester lining
This is the benchmark for high-end cars. OEMs like Aston Martin, Jaguar, and Maserati use Sonnenland A5, and it’s widely considered the premium option.
Pros
- Luxury OEM look and feel
- Exceptional abrasion resistance and long lifespan
- Rubber core has enhanced acoustic properties
- Holds up for many years with proper care
Cons
- One of the most expensive fabrics available
- More rigid due to the dense rubber core than Stayfast or Twillfast RPC
- Imported, which can make sourcing trickier
Installer’s Note: A5 delivers unmatched appearance and durability, but its stiffness can create challenges. It’s the right call for luxury restorations and show cars, but often more material than a daily driver needs.
Twillfast RPC ($$)
Made by: Haartz (U.S.), produced in the U.S.A.
Build: Similar three-ply structure, stretchier and more flexible than A5
Twillfast RPC is a favorite among trimmers. It offers nearly the same quality as A5, but with easier handling and a lower price point.
Pros
- OEM grade — used on BMW, VW, Jeep, Mini, Chevrolet, Ford, and more
- Flexible structure makes installation smoother and reduces frame stress
- Good acoustic insulation for a quieter ride
- UV and mildew resistant, performs well in different climates
Cons
- Still a premium option compared to budget fabrics
- Sometimes marketed under different names (RPC, Twillfast II)
Installer’s Note: RPC’s flexibility makes a huge difference. Many tops are cut intentionally tight, then stretch perfectly into place. This reduces stress on the frame and delivers a snug, factory-quality finish.
Sonnenland A5 vs. Twillfast RPC
On paper, these two look almost identical. Both are three-ply, both use an acrylic twill face, rubber core, and polyester backing. Both are OEM-approved and built for longevity.
The real difference is in how they’re made:
- Sonnenland A5 is knife-coated, which creates stiffness. It feels premium but is harder to work with and tougher on frames over time.
- Twillfast RPC is extrusion-coated, making it more flexible. That flexibility means easier installs, less stress on hardware, and a cleaner break-in process.
Bottom line: A5 is the luxury pick, but RPC is the more practical option for most daily drivers and restorations.
Stayfast ($)
Made by: Haartz (U.S.), produced in the U.S.A.
Build: Acrylic square weave outer, rubber core, cotton backing
Stayfast is the tried-and-true budget choice. It doesn’t look as refined as modern twill fabrics, but it’s dependable and easy to source.
Pros
- Affordable compared to A5 and RPC
- OEM quality — used on models like the Mazda Miata
- Performs well in mild climates and light use cases
- More color options offer enhanced customization
Cons
- Cotton backing has less UV resistance than polyester
- Louder cabin with less insulation
- More basic look and feel
Installer’s Note: Stayfast makes sense for budget restorations, classics, and fair-weather drivers. It won’t deliver the premium look or longevity of A5 or RPC, but it fills an important role in the market.
Final Thoughts
There’s no one-size-fits-all answer to convertible top fabrics — the choice depends on the project:
- Sonnenland A5 → unmatched luxury and durability for high-end builds
- Twillfast RPC → the best all-around balance of cost, performance, and installer-friendliness
- Stayfast → budget-friendly option for restorations and mild-weather vehicles
For most installs, Twillfast RPC checks the most boxes. It delivers OEM quality, looks great, installs easier, and holds up well long-term. But whichever option you choose, all three come from Haartz — the industry leader in convertible topping fabrics.
At OEM+ Auto Tops, we work exclusively with Haartz materials to ensure every top we produce meets OEM-grade standards for quality and performance. To learn more about our products or register for our local installer network, visit oemplusautotops.com. You can also follow us on Facebook, Instagram, and YouTube for updates, tips, and shop insights.
Recent Comments