304 vs 316 Stainless Steel for Restraints

Every useful listing for a steel collar or cuff should name a grade when the source supports one. “Stainless steel” alone covers several alloys with different properties. If a piece is going to close on a wrist or throat, grade and finish are worth understanding—but an undocumented number is worse than an honest omission. Here is what the common numbers mean and how this store reports them.

What the grades actually are

Stainless steel resists corrosion because chromium in the alloy forms an invisible oxide layer on the surface. The three grades you meet in this category differ mostly in what else is in the mix:

• 201 — the budget alloy. Less nickel, more manganese. It looks like stainless in the shop and spots with rust after real contact with sweat or body fluids. Anything unmarked and unusually cheap is almost always 201. Avoid it for anything worn against skin.
• 304 — the workhorse austenitic stainless, roughly 18% chromium and 8–10% nickel. Corrosion-resistant, and the same family used for cutlery, kitchen surfaces and quality watch cases. It is usually described as non-magnetic, and in the annealed state it very nearly is; cold working, machining and welding can leave a finished part slightly magnetic, so a magnet catching faintly on an edge does not by itself mean you have been sold something else. This is what a serious metal restraint should be made from — and what most, though not all, of our range is. Where a piece is not 304 we say so on its own page: the Eclipse collar is polished zinc alloy, the Atlas frame is powder-coated steel, and the Cardinal, the Ballast and the Tempest clamps are stainless of a grade the makers have not yet confirmed to us in writing. We would rather list the exceptions than let one number cover the shelf.
• 316 / 316L — adds molybdenum for extra resistance to chlorides and salt. It is the marine and surgical grade; the "L" means low-carbon for welding. Genuinely better in seawater or an operating theatre, marginally better against skin, and noticeably more expensive.

The honest answer on 316

You will see fetish pieces marketed as "316L surgical steel" at a premium. For a collar or cuff worn indoors, the practical difference over well-finished, passivated 304 is small. What actually protects your skin is not the last percent of the alloy but the surface: a properly finished and passivated 304 piece presents a stable chromium-oxide layer, and that layer is what your skin touches. A rough or unpassivated 316 piece can behave worse than a well-made 304 one. Grade matters; finish matters as much.

Several pieces in the collection are listed as 304 where that grade is present in the source specification. Other stainless pieces have no exact grade confirmed, and the Eclipse is zinc alloy rather than stainless. The individual product page is the authority; this guide does not lend 304 from one product to another.

On nickel

The reassuring-sounding claim "low nickel" or "nickel-free" is usually wrong. Austenitic stainless steels contain nickel — around 8–10% in 304 — and it is part of what makes them corrosion-resistant and non-magnetic. What matters for skin is not how much nickel the alloy contains but how much it releases, and a passivated stainless surface releases very little. That is why surgical instruments and good watch cases come from the same family of alloys. If someone has a diagnosed severe nickel allergy, no austenitic stainless is truly safe against broken or long-occluded skin — that is a medical question, not a marketing one.

What to look for when you buy

• A named grade — 304 at minimum. "Stainless" with no number is not proof of anything, and a seller who cannot tell you the grade has not asked their maker. Where we are in that position ourselves — the Cardinal, the Ballast and the Tempest clamps — we print it on the page rather than borrowing the number from the pieces next to them.
• A finish that is polished or brushed and passivated, not just tumbled.
• Edges radiused and deburred where they meet skin.
• A seller willing to tell you which is which. We list the grade on every product page.

The short version: buy 304 that is finished properly, not 201 dressed up, and don't pay a 316 premium for a room-temperature difference. Once the grade and the finish are right, the rest is fit — which is its own five-minute job.