Stainless Steel Sink Specifications: Gauge, Radius, Drain and Finish

Quick answer: a stainless steel sink specification is decided by six numbers — steel grade (304 or 316), thickness (16 gauge = 1.5 mm, 18 gauge = 1.2 mm), corner radius (R0 or R10), drain opening (90 mm for North America, 110 mm for parts of Europe and Asia), bowl depth (200–250 mm) and installation type (undermount, topmount or flush). Get those six into the purchase order and most sourcing disputes never happen. Fengyin builds 145 base models in SUS304/SUS316, MOQ 30 pieces per model, 25–35 days production.

Specification at a glance

On this page

• Material: 304 or 316 stainless steel
• Thickness and gauge: 16G, 18G, 20G
• Corner radius: R0, R10, R15 or R25
• Bowl depth and capacity
• Drain opening and position
• Installation: undermount, topmount, flush
• Finish options and what they survive
• Sound damping and condensation control
• Packaging and container loading
• Certification and documentation by market
• How to write a sink specification that survives production
• Sourcing questions

Material: 304 or 316 stainless steel

Almost every sink we build starts as SUS304 (18% chromium, 8% nickel). It resists food acids, most household chemicals and normal tap water without pitting, and it is the grade specified by the majority of importers for residential kitchens.

SUS316 adds 2–3% molybdenum. That addition is what makes it resist chlorides — salt spray, coastal air, heavy sanitising chemicals, marine and food-processing environments. If your market is a coastal city, a cruise or marine programme, or a commercial kitchen that gets hosed down with chlorinated sanitiser daily, 316 is the correct choice, not a premium upsell.

What we do not do is sell 201 as 304. Cheaper 201 sheet is common in this industry and it shows up as rust at the weld within one or two seasons. If a quotation is far below the market, ask which grade the sheet actually is and whether the mill certificate travels with the container.

Thickness and gauge: 16G, 18G, 20G

Gauge is the single most quoted number in sink sourcing, and the single most misunderstood. Lower gauge means thicker steel:

Two things buyers get caught by. First, a supplier may quote 16 gauge and ship 1.2 mm, because “gauge” is sometimes used loosely. Ask for the millimetre figure on the purchase order. Second, thickness at the rim is not the same as thickness at the bowl floor — drawing thins the sheet, so a 1.2 mm drawn sink can measure under 1.0 mm at the bottom. We state both numbers on request.

Corner radius: R0, R10, R15 or R25

The corner radius is how sharp the inside corners of the bowl are. R0 is a near-square corner, R10 has a 10 mm curve, R25 is noticeably rounded.

R0 looks modern and maximises usable floor area, which is why it dominates the North American and Australian undermount market. The trade-off is real: crumbs and grease collect in a tight corner and need a cloth or brush, not a wipe.

R10 is the practical compromise that most European and Asian buyers choose. It still reads as a square sink from standing height, but a sponge passes through the corner without stopping.

R15 and R25 belong to value lines and to markets where cleaning speed matters more than the visual edge — rental apartments, serviced accommodation, canteens.

Radius also changes tooling. Switching a drawn sink from R10 to R0 means a new mould, so it is a programme decision, not a line-item option. On handmade sinks the radius is set by the weld and the grind, so it can be changed within the same order.

Bowl depth and capacity

Bowl depth is where complaints come from two years after delivery. A 180 mm bowl cannot hide a stock pot; a 250 mm bowl in a 600 mm base cabinet leaves no room for the trap.

Our handmade programmes run 200 mm to 250 mm of internal depth, with 220 mm as the common specification. As a rule of thumb for a residential kitchen: 200–220 mm covers plates, pans and a colander; 230–250 mm is for buyers who cook with large stock pots or wash baking trays flat.

Exterior size and interior capacity are different numbers, and this is where most specification errors happen. A sink described as 1200×480 mm may have a bowl of 395×350 mm once the rim, the divider and the radius are accounted for. We publish both figures for every model in the dimension table precisely so this does not need to be guessed.

Drain opening and position

Two drain standards cover most of the world. 3½ inch (90 mm) is the North American opening and fits standard basket strainers and garbage disposal flanges. 110 mm is common on European and some Asian models, often paired with a different strainer body.

Get this wrong and the sink arrives unusable — the strainer will not seat, or a disposal will not mount. It cannot be corrected on site without a plumber and a stainless fabricator, so it belongs in the purchase order, not in an email thread.

Position matters as much as size. Centre drain is the default. Rear-set drains free up cabinet space under the bowl for a waste bin or a drawer, and they are standard in the North American market. Offset drains appear on double bowls where one side is used for prep. If the sink sits above a dishwasher or a disposal, confirm the drain position against the cabinet drawing before production, not after.

Installation: undermount, topmount, flush

Undermount fixes the bowl below the counter, so crumbs wipe straight in and the countertop reads as one surface. It needs a solid-surface, quartz or stone top and a fabricator who can cut and polish the opening. Most of our handmade range is specified undermount for this reason.

Topmount (drop-in) sits on the counter with a visible rim. It is cheaper to install, forgiving of cutout tolerance, and it is still the majority choice for renovation and rental work. The rim is also a place where water sits, so the sealant bead matters.

Flush mount sits level with the counter. It looks closest to a seamless surface but demands the tightest cutout tolerance of the three, and it is the least forgiving if the counter is not flat.

Cutout tolerance is the number to agree before ordering: our undermount rims are held to under 2 mm of flatness, and mounting clips are adjustable for countertop thickness from 20 to 40 mm. The cutout guide covers how to convert an outer size into a template.

Finish options and what they survive

Satin / brushed is the workhorse. It hides water spots and light scratches, it can be re-brushed on site, and it is the safest choice for a distributor who does not want finish complaints.

Mirror polish is a showroom finish. It shows every fingerprint and every scratch, and it needs care instructions in the box.

PVD (gold, rose gold, gunmetal, black) is a vacuum-deposited layer, not paint. It survives normal kitchen use far better than electroplating, but it is not indestructible: abrasive pads and bleach-based cleaners will dull it.

Nano coating is a thin anti-oil layer applied over brushed steel. Water beads and oil wipes off more easily for the first year or two. Treat it as a convenience, not a permanent property — and do not sell it as scratch protection.

Whichever finish you choose, approve a physical sample before mass production. Colour on a screen and colour under a customer’s kitchen light are two different things, especially on black and gunmetal. The finishes guide goes deeper on each option.

Sound damping and condensation control

Stainless steel rings. A sink without damping sounds thin and transmits the noise of running water and crockery into the cabinet. Two things fix it: EVA sound pads bonded to the underside, and an anti-condensation coating that stops cold steel from sweating in humid kitchens.

Pad coverage is the number that separates suppliers. Some cover 30–40% of the base and call it damped; better programmes cover 80% or more across the base and the sides. Condensation coating matters more than buyers expect: without it, moisture drips onto the cabinet floor and the failure appears as swollen board, months later, with no obvious cause.

Both add cost and are easy to leave out of a quotation. Ask for the coverage percentage and whether the coating covers the full underside.

Packaging and container loading

For an importer, packaging is a freight decision disguised as a packing decision. A sink shipped in its own carton with foam corners uses volume that a nested pallet does not.

Nested packing stacks bowls inside each other with protective interleaves and packs the accessories separately. On suitable models it can raise the quantity per container by roughly 40% against individual boxing. The trade-off is handling at the destination: nested pallets suit a distributor with a warehouse, not a retailer who needs shelf-ready cartons.

Retail-ready packing puts the sink, strainer, grid, cutout template and instructions in one printed carton with a barcode. It costs more per unit and loads fewer pieces, but it can go straight to a shelf or an e-commerce pick line.

The right answer depends on your channel. Tell us the destination port, the channel and whether you break bulk, and the loading plan follows from that. A 20ft container of 1200 mm double bowls and a 40HQ of nested single bowls are completely different freight maths.

Certification and documentation by market

This is the section where most supplier pages overclaim, so here is the honest position.

Stainless steel sinks are not electrical appliances. Marks such as CE, GS, ETL or CB are not the natural certification path for a sink; they belong to appliances. What actually gets asked for is different by market: cUPC (ASME A112.19.3 / CSA B45.4) for North America, EN 13310 performance documentation for Europe, and material or dimensional test reports elsewhere.

What we supply as standard: material grade declaration, dimensional drawings, and third-party test reports from CMA/CNAS-accredited laboratories on request. What we do not do is print a certification logo on a carton for a model that has not been tested — if you need cUPC or EN 13310 on a specific model, raise it before quotation and we will confirm the actual scope, in writing, for that model.

If a competitor sends you a catalogue of certificates covering every product line, that is worth a second question.

How to write a sink specification that survives production

Most sourcing disputes are not quality disputes. They are specification gaps. A complete line item answers nine questions:

Send us a drawing, a sample or a competitor model and we will return the completed line with the gaps flagged. That is faster than a quotation built on assumptions.

Sourcing questions

What is the most common cause of a sink complaint?

A specification gap, not a manufacturing defect: drain size, drain position or bowl depth agreed verbally and never written into the purchase order. Thickness quoted in “gauge” rather than millimetres is the second most common.

Is 16 gauge worth the extra cost over 18 gauge?

On handmade sinks above roughly 900 mm, yes — the bowl holds its shape and the rim stays flat. On small drawn sinks the difference in use is hard to feel, and 18 gauge is the sensible value choice.

Do you supply cUPC or EN 13310 certified sinks?

Certification is per model, not per supplier. Tell us the model and the destination market and we will confirm the actual status in writing before quotation. We will not print a logo on a carton for an untested model.

Can you change the corner radius on an existing model?

On handmade sinks, yes — the radius is set by weld and grind. On drawn sinks it requires a new mould, which is a programme decision with tooling cost and lead time.

How many sinks fit in a container?

It depends on the model and the packing method. Nested packing can raise the count by around 40% versus individual cartons on suitable models. Send the model list and destination port and we will return a loading plan.

What is your MOQ and lead time?

30 pieces per model, with 25–35 days production for a 20ft container after drawing and sample approval. Mixed models can be consolidated in one container.

Check the numbers against a real model

Every specification above is easier to judge against a concrete size. Our dimension table lists outer size and bowl size in millimetres for all 145 base models, grouped by series. The product catalogue shows finishes and configurations, and the cutout guide converts an outer size into a countertop template.

For lead time, payment terms and what we can document, see how to verify us as a supplier. Send a drawing or a competitor model to our sales team and we will return the completed specification line with any gaps flagged — usually within one working day.

Two decisions that follow from this

• Handmade vs pressed sink — tooling and size flexibility
• Undermount vs topmount vs flush mount — countertop and cutout
• 16 gauge vs 18 gauge — which wall thickness to choose

Published October 2026. Figures reflect current Fengyin production standards; confirm the exact value per model before placing an order.