Batch cooking is a storage problem wearing a cooking costume. You cook once. The other eleven meals are just sitting somewhere, waiting, and whatever they're sitting in decides how they turn out.
Steel is good at the freezer part and no good at all at one specific step. Here's both.
Why steel is fine in a freezer
Cold is the easy part. Steel doesn't go brittle at freezer temperatures the way plastic does, and it doesn't shatter the way glass can when something frozen gets knocked. A container that goes in the freezer forty times a year for a decade is exactly the job steel is for — we guarantee the steel for ten years, rust included.
It also conducts heat well, which cuts both ways. Food freezes faster in steel and thaws faster in it. Faster freezing is genuinely useful — it's smaller ice crystals and better texture on the other side.
The part we have to be blunt about
Never put a steel container in a microwave. Not for a few seconds, not to "take the chill off." Steel reflects microwaves rather than absorbing them, and metal in a microwave can arc. This isn't a preference or a warranty technicality — don't do it.
So the reheat is a hob, an oven, or a plate. You take the food out of the container and put it in something else. That's a real cost, it's on you every single time, and if you reheat at a desk with nothing but a microwave then steel is the wrong container for your lunch and we'd rather say so.
The longer version of what "microwave-safe" is even claiming is worth reading if this is the deciding factor.
Thawing, honestly
Fridge overnight is the answer. Steel helps here — it pulls heat in evenly, so you don't get the thawed-edges-frozen-middle problem.
The body can go in an oven once the lid is off. The lid should not: it carries a food-grade silicone seal, and an oven is not what that seal is for. Lid off, oven on. And a frozen container going into a hot oven is a thermal shock question we'd rather you didn't test — thaw first.
Two things that actually go wrong
Headspace. Liquid expands when it freezes. Fill a container to the rim with soup and the seal is what absorbs it. Leave a couple of centimetres. This is the single most common way people are disappointed by a freezer container, in any material.
You can't see in. Steel is opaque. Three months later, every container in the freezer is a small mystery, and the honest answer is that you have to label them. A strip of tape and a pen. We don't sell a clever solution to this, and we're not going to pretend the problem isn't there.
Sizes, for what it's worth
Portions are the whole point of batch cooking, so the size is the decision. The 400 ml round is a single portion of most things. The 800 ml rectangular is a full meal and stacks flat. The 1200 ml and 1400 ml are for the cook-once-eat-four jobs — a tray of chilli, a batch of ragu.
Rectangles stack without wasting freezer space. Rounds are better for anything wet.
Two materials, both named
304 stainless steel and one food-grade silicone seal. That's the entire list, lid included — no polypropylene closing it. You can read exactly what touches your food, gaps and all.
The seal is the part that wears out first, especially with heavy freezer use, so we sell it separately rather than let a worn ring end the whole container.
Replace the plastic.
Food should be stored without doubt.