One Button, Lids From One Inch to Four, a Battery the Listing Calls Eighty Jars and the Manual Calls Thirty, and Two Lids in My Kitchen It Could Not Open. I Counted.

I have opened the same pickle jar every Sunday for forty-one years. Two hands, a rubber grip mat, hot water on the lid, and on the bad Sundays, a knock on the neighbor's door.

That was the whole toolkit.

Then my daughter gave me a box the size of a toaster, and inside it was eight ounces of black plastic with one button.

This page is what I found when I read the manual, counted the jars, and checked the numbers against the listing.

Because they don't match.

Nothing to Assemble, One Button, and It Stops by Itself

You take it out of the box, and there is nothing to assemble. That's the first thing I checked, because I own a mandoline with eleven parts and a temper.

The shape is a cone, wide at the top, with a skirt of rubber ribs inside. You set it over the lid, let it sit flat, and press the button once.

Inside, two rings close on the jar — one grips the lid, one grips the glass below it — and the top ring turns. The motor stops on its own when the lid gives.

The whole event takes about six seconds, and it is quieter than my electric kettle.

The honest part of this machine is the stopping. It doesn't keep twisting. It lets go, and it doesn't need a second button to do it.

One Inch to Four, and the Two Shapes It Doesn't Do

The manual says lids from one to four inches across.

I measured what that means in a real kitchen. A regular mason jar is about two and three-quarters. A pasta-sauce jar is about three and a quarter. The big pickle jar is three and seven-eighths, and it fits with room to spare.

Four inches covers most of the pantry. What it doesn't cover is shape.

The skirt needs a round lid sitting on a round jar, with an inch of clear glass below the lid for the lower grip.

A square jam jar: no. A jug with a handle in the way: no. A jar whose neck is shorter than an inch: the grip has nothing to hold.

Eighty Jars in the Listing, Thirty in the Manual

The listing, in its description, says "up to 80 jars per charge."

The manual says "approximately 30 cycles per charge."

Those can't both be true.

So I charged it once — two hours, the light went from red to green — kept a pencil in the kitchen drawer, and made a mark for every lid.

Thirty-four jars, and the thirty-fifth is where it started to sound patient instead of sure.

At three stubborn jars a week, one charge is a season.

By the manual's own arithmetic, the listing's eighty is a number I couldn't make the machine produce.

The Two Lids That Beat It

The first was the childproof cap on the pharmacy bottle — too tall for the cone. The skirt sat on the shoulders of the cap and never reached the lid. The manual is honest about this one; the listing isn't.

The second was my sister's square jam jar, the one with the cloth on top.

Two lids out of thirty-six is a record no rubber mat of mine ever managed.

I'm keeping both lids on the counter anyway, out of respect.

What the Honest Complaints Say, and Whether They're Right

I read the reviews the way I read the label — looking for the complaint that did the arithmetic.

The most useful one is four stars: "Opens everything in my kitchen except the tall bottle of vanilla extract. Wish it was taller." She's right about the height. The cone is what it is.

The one-star reviews are mostly about the charge — "didn't hold a charge after two months" — and the maker's answer is printed under each one: replace under the one-year warranty, and they send the label.

I can't test two months in an afternoon. What I can say is that the warranty is printed on the box, with an address, and the manual asks you to register nothing.

Eight Ounces, Wipe Clean, Don't Drown It

The weight is the one thing to know before you order. Eight ounces is nothing to carry. It is something to hold steady on a tall jar with one hand, if the other hand is busy.

The manual's care page is four sentences: wipe it with a damp cloth, don't put it in the dishwasher, don't hold it under water, charge it once a month even if you haven't used it.

That last sentence is the one most people will skip, and the one-star reviews suggest some did.

Who It's For

If your kitchen has round jars and a drawer of failed rubber mats, and you want one button and no assembly, and you can live with two lids that beat it and a battery that's a season, not a year —

Then it's worth one, and the arithmetic is on this page.

Not because of the number in the listing.

Because you'll know exactly what it opens, exactly what it doesn't, and exactly when to charge it.

P.S. — If you take one thing from this page, take the two numbers. Thirty jars on a charge, and one to four inches across. Everything else about this machine sits between those two.

P.P.S. — If a lid ever comes off with a hiss and a smell, that's a jar gone bad, not a wrist gone bad. Open it in the sink and throw the contents out. No machine should talk you out of that.

P.P.P.S. — And if you do order it, keep the pencil in the drawer. When the charge runs out you'll have thirty-some marks on paper, and that's how you'll know the listing's eighty was never yours.