Convertible Tops: Buy the Cloth, Source the Hardware

Because the market has converged, and the convergence is a good one. Haartz Corporation traces its North American operations to 1922, when John Haartz introduced a three-ply mohair all-weather convertible topping, and has been headquartered in Acton, Massachusetts since 1966. Haartz describes Stayfast as an acrylic square weave facing over a rubber inner layer with a cotton backing, made in the USA and formerly specified for original equipment over many decades; Twillfast RPC as an acoustically enhanced three-ply composite — acrylic twill weave face, crease-resistant butyl rubber inner layer, polyester dobby backing — 1.35 mm thick, stocked at 60 inches wide, also made in the USA. The trade publication The Hog Ring places Sonnenland A5 at the premium end (knife-coated, stiffer, harder to work with), Twillfast RPC as the OEM-grade middle and Stayfast as the entry tier.

This matters for correctness, not just price, because of weave history. Haartz's own Vintage Restorer's Guide records that duck, or square weave, dominated as the face fabric on cloth topping for many years, and that twill became a favourite only from the 1980s. Put a modern twill top on a car that wore a square weave and it is wrong in a way any judge sees the first time it parks beside a correct car. So: buy the cloth everyone buys, in the weave the car should wear.

The unglamorous ones, which is most of them. A top frame is stamped brackets, bent tube, welded joints and a plated finish. The latch is a die-casting with a cam, a spring and a striker. The pivots are turned pins in bronze or nylon bushings. The frame screws are cold-formed fasteners in head styles that left hardware stores decades ago. Restorers currently solve these by cutting bushings from bar stock and hunting swap meets for screws — a recurring theme on marque forums, and a reliable sign that the parts exist as a need but not as a product.

That is a Taiwanese factory's home ground, and it connects to two capabilities we have covered elsewhere: the plating stack behind any bright latch or exposed casting, and the fastener trade that will run a non-standard head style at a sane quantity. A frame hardware kit for one platform is a few dozen small tooled parts across four or five processes — a real project for a mid-sized supplier here, an unattractive one for a US house.

On duty: none of this lands in the textile headings. Body hardware for motor vehicles commonly classifies in 8708.29 at 2.5 percent Column 1, read live from the USITC database on 3 August 2026, though hydraulics, fasteners and castings classify elsewhere by function and material. What decides landed cost is whether the classification is on the Section 232 auto-parts list: Taiwan-origin parts on it enter at a capped 15 percent total, parts off it pay 10 percent under the Section 301 forced-labour action. We could not verify that list from the primary document, so it belongs in the first email to your broker.

It says the parts are the minority of the invoice, and that this decides whether sourcing is worth doing at all. A top job is measured in shop days: strip the old top, deal with pads and tack rails that are usually shot, address frame rust and slop, fit and stretch the new topping, chase leaks. The material and the mechanism are inputs; the labour is the job.

For scale, the US Bureau of Labor Statistics puts the national mean hourly wage for Upholsterers (occupation 51-6093) at $22.76, with a mean annual wage of $47,340, in its May 2025 Occupational Employment and Wage Statistics estimates. That is the worker's wage, not what a shop bills — a trim shop's door rate carries premises, insurance, tooling, consumables and margin on top, and the multiple varies by region. Treat it as the floor of the cost stack, not a shop rate.

The conclusion is uncomfortable but clean. Shaving cost off a mechanism does almost nothing for a shop doing one or two cars a year: you move a small fraction of a large invoice while taking on sample loops, tooling risk and a supplier with no track record on your platform. The same saving repeated across a production run, by a brand that intends to sell frame hardware kits for years, is a business. Sourcing here is a volume decision, not a per-car one.

More than most buyers assume. FMVSS 302, at 49 CFR 571.302, covers materials in the occupant compartments of motor vehicles, and S4.1 names convertible tops explicitly among the covered components, alongside seat cushions, headlining, arm rests, trim panels, floor coverings and sun visors. S4.2 then draws the line by geometry rather than part name: any portion of a single or composite material within 13 mm of the occupant compartment air space must comply, tested as a composite where layers adhere at every point of contact — which pulls the well liner, the boot lining, the top pads and the inner layers of the topping stack into scope. The bar: the material shall not burn, nor transmit a flame front across its surface, at more than 102 mm per minute, with a specimen that stops within 60 seconds and 51 mm treated as passing. Ask for the report on the actual construction; the standard tests composites as built.

When you are buying for one car, or two. The US specialists here have been at it for decades — Hydro-E-Lectric, now trading as Convertible HQ out of Punta Gorda, Florida, states it has been in business since 1976 and runs repair-and-rebuild services alongside published technical-support articles for exactly the bleeding and installation problems that sink a first hydraulic job. An unproven overseas motor-pump at a quantity of one gives you none of that and a lead time in months. Much frame work is repair anyway: if your original is straight it wants a bushing kit and a rebuild, and the used market plus a competent fabricator is your whole supply chain.

Sourcing earns its keep in the repeat case: a reproduction brand or marque specialist committing to a run of frame hardware kits, latch sets or pivot and bushing kits for a platform with enough surviving cars to justify tooling. If that is you, describe the parts on our request page — vehicle, years, body style, which components, what samples you can supply. Taiwan Supplier Hub returns a shortlist of at least three verified manufacturers that have confirmed they want the project within 14 days, US$99 at launch, refunded if we can't deliver. Ask us to source the cloth too and we will tell you to buy it from the mill everyone else does.