China makes the vast majority of the world's vacuum-insulated drinkware, and the Yongkang–Jinhua industrial belt in Zhejiang alone hosts thousands of factories. Choice is not the problem — telling a real factory from a trading company (or a broker with a nice website) is. Here are the 7 checks we recommend every buyer run before wiring a deposit.
Ask for the company's business license and check it on the official National Enterprise Credit Information system. Look at two things: the registered scope (does it actually include manufacturing, or only "trading"?) and the registered capital. A license that says "wholesale and trade" is your first clue you are talking to a middleman.
Any real manufacturer will happily do a live video walk-through of the production floor. Ask to see the vacuum-forming and welding stations, the powder-coating line, and the assembly area — in one continuous shot. Trading companies usually "walk" you through someone else's plant or stall with a bad connection.
Two bottles that look identical can perform very differently. Ask the supplier to state temperature retention figures by test standard (e.g. 95°C water, 6 hours, ≥ 55°C) and to provide test reports. Then verify with a sample: fill it, wait, measure. Real factories publish real numbers because they control the vacuum process.
Depending on your market you will need some combination of FDA, LFGB, CA Prop 65, and food-contact certificates for both the stainless steel and the plastic components (lids, gaskets, straws). A factory keeps these on file and sends them in a day. A trader has to chase its own supplier — and you find out at customs.
Ask specifically: what is the AQL standard for the final inspection? Is leak-testing done on 100% of units or by sampling? How are vacuum failures screened out? Real manufacturers answer in specifics — "2.5 AQL, 100% leak test with pressure gauge, vacuum drop test per batch."
Unit price depends on: capacity, wall finishing (powder coat, spray, mirror), lid type, decoration (silk-screen, laser engraving, heat transfer), and packaging. Get an itemized quotation, not one number. Itemized quotes also let you compare factories apples-to-apples and spot where one supplier is padding.
Chargeable samples (refunded against bulk orders) filter out serious suppliers on both sides. Before placing a trial order, agree in writing on Incoterms (usually FOB Ningbo or FOB Shanghai), lead time, payment split, and what happens if the inspection fails.
Yongkang and the surrounding Jinhua region is the densest drinkware manufacturing cluster in the world — which means deep supply chains, fast tooling, and competitive pricing, but also a lot of intermediaries. The checks above take a day to run and will save you a container of problems.
SSMug is a manufacturer based in Yongkang. We welcome video audits, share compliance files upfront, and quote itemized price tiers. Send us your project and compare us against any supplier on your list.