You deal with a US-based company and one person who owns the outcome — the quote, the sample, and the answer when something needs fixing. Most companies that do this are brokers who mark up an invoice and disappear once the container clears. We came the other way around — from the factory floor.
What you get is a single American counterparty who takes the parts of sourcing you don't want — supplier vetting, quality, and documentation, with one accountable contact in US business hours. Not access to a factory, and not a broker's markup.

China-plus-one usually means standing up a second supplier in another country — requalifying parts, re-running tests, re-listing a UL file. We skip that: we already hold deep, working relationships with qualified lines in both Vietnam and China, running one drawing set and one test procedure. You elect the country of origin on the purchase order; there is no second vendor to qualify, and nothing to explain to your own customer.
One engineering system, two origins
| Role | Primary line | China-plus-one |
|---|---|---|
| Operations | Winding, SMT, final assembly, and test under one roof. | Winding, SMT, final assembly, and test under one roof. |
| Country of origin | CN | VN |
Same drawings, same UL file, same test reports. When the tariff schedule moves, volume moves between the lines — nothing to requalify. For the duty and landed-cost math by HTS code, see the duty stack →
We came up in manufacturing, so we qualify every supplier behind a Kestner order the way your own auditor would — a line walk, the test data, the mill certificates for magnetics and copper — and only sell what we can inspect, warrant, and RMA. When something is not a fit, we say so on the first call.

Every factory clears the same bar before it gets a Kestner order — the checks a good plant passes at each audit. If a supplier can't clear them, we don't quote it.
The line, walked
We watch the process run on the floor — not a sales showroom. If we can't see it built, it doesn't qualify.
Test capability, proven
The right gear on site — ICT, hi-pot, aging, pull-force — and its real data, read against your spec, not a generic report.
Materials, traced
Mill and material certificates for the inputs that matter — magnetics, copper, enclosures — that a transshipper can't paper over.
Certifications, verified
Safety and compliance marks confirmed by file number at the source, plus the ISO and BSCI systems behind them.
A sample, approved
A production-representative sample tested to your requirements and signed off before a single unit is built.
Capacity & continuity
Enough capacity for your volume, a stable operation behind it, and a second line or origin where it matters.
Product, spec, target volume, certification, and destination.
One business day for standard SKUs, three for custom. If we can't supply it, we say so.
Approved before a production run.
Built in Vietnam or China — your election — origin documented per unit.
Ships with every order (below).
Today
On the roadmap
Ask where we are today.
China-plus-one is a supply-chain strategy where a buyer keeps China capacity but adds a second country — often Vietnam — to reduce tariff and concentration risk. With Kestner the second origin is already built: we run the same drawing set at qualified lines in both Vietnam and China, so you choose the origin without standing up a new supplier.
Yes. The same part number builds on either line under one engineering system and one test procedure. You elect the country of origin on the purchase order; the UL file and drawings do not change.
The supplier. Kestner is a US-based counterparty you buy from — not a commission agent who introduces you to a factory and steps aside. We quote, sample, warrant, and stand behind the order.
Today, you or your customs broker are the importer of record; we document the country of origin, HTS classification, and the substantial-transformation basis so entry is clean. Taking title as importer of record with DDP, duty-paid delivery is on our roadmap — ask where we are.
At qualified partner lines in Vietnam and China, under one engineering system and one test procedure. You choose the country of origin.
Tell us what you're sourcing and where you are today. A person answers — usually within one business day.