An MIT Engineer Invented a Strange Dumbbell in His Garage. Then It Made Him Jacked.

He could not buy the training tool he wanted, so he printed it. Hundreds of times, on a table in a rented house, until one version stopped breaking.

Ryan Maddox

Staff writer · August 31, 2026 · 8 min read

Kensui AdaptaBELL PRO

This is the dumbbell he invented: two knurled handles, about 2 lb bare, that screw onto the plates every gym already has. $49 a pair, 140 lb across the pair.

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It Started in a Rented House With No Gym in It

Remy Mock spent years as a digital nomad, moving between countries with whatever training gear fit in a bag. Dumbbells do not fit in a bag. Nothing about a dumbbell was ever designed to travel, and nothing about a hotel gym was designed for someone who wants to get seriously strong.

For a while he worked around it with a dip belt, which hangs ordinary gym plates off a chain at your waist. That solves pull-ups and dips and very little else.

The dip belt is where the whole idea starts. Plates are everywhere, they are stamped with honest numbers, and somebody else already bought them. All that was missing was something else to hang them on.

This is the whole problem in one room. Plates and a doorway bar travel or can be bought anywhere. The thing that turns them into a dumbbell did not exist.

The Garage Came First

Kensui, the company that grew out of all this, dates its own founding to a garage workshop in 2019. Mock is not a gear designer by training, so the workshop had to teach him the job.

He ran hundreds of designs through a desktop 3D printer, which is the one part of this that scales for a person with no factory.

A printer hands you a part overnight for the price of the filament. It will not tell you which part is right, and that only comes from making the wrong ones.

Almost all of them are wrong. That pile is the actual job, and it is the reason a screw thread that holds 140 lb without loosening took hundreds of tries rather than one.

The Engineer Who Had No Business Fixing This

Mock holds two engineering degrees from MIT and swam at an All-American level. None of that is industrial design, so he taught himself CAD from scratch and started drawing.

The company took the name Kensui, which means pull-ups in Japanese. Its stated rule is that it only sells equipment the people who made it actually train with, which is an easy thing to claim and a slightly harder thing to build a product line around.

“Steel Is Overkill”

Here is the sentence that explains the design better than any spec sheet does.

Most adjustable dumbbells are heavy before you put anything on them. The mechanism is the product, so the mechanism is where the money and the mass go. You pay for five to ten pounds of selector hardware you never asked for, and you pay several hundred dollars for the privilege.

His handle goes the other way. It is a knurled body with a screw thread at each end and a collar that spins down against the plates. Bare, the pair weighs about two pounds. No selector, no dock, no proprietary block, almost nothing to break.

1. The weight is already in the room. Standard 28mm and 50mm plates both fit the same handle, so whatever is on your floor works and there is nothing to reorder.
2. You always know the number. Plates are stamped. A tool that cannot tell you what you just lifted is a tool you cannot program around.
3. The ceiling moves with you. More capacity just means more plates, which is why the top model reaches 300 lb across the pair while the empty handles still weigh about two pounds.

The Short Version

A dumbbell is a handle with weight fixed to both ends. That has been the entire idea for roughly 2,500 years, and the only real change since is that some of them now have a selector pin. What came out of that workshop ends in a screw thread instead, so you load the plates that are already on the floor.

Kensui price, capacity and rating verified on the product page, August 31, 2026. The two comparison columns describe the two shapes the rest of the category comes in rather than any one competitor.

The Part That Does the Work

Bare, it looks like a bolt. That is the honest description and it is the reason people scroll past these things. Loaded, the shape disappears and it behaves like a dumbbell that happens to have no upper limit.

The $49 PRO is a reinforced polymer body rated to 140 lb across the pair, which is 70 lb in each hand. There is a $149 MAX in machined aluminium that doubles the ceiling to 300 lb, and it is out of stock as we publish this, so the PRO is the one you can actually put in a cart today.

Changing weight is slower than a selector pin and faster than most people expect. You spin off a collar, swap plates, spin it back on, then do the other hand.

Kensui AdaptaBELL PRO

The handle this story is about. $49 a pair, 140 lb across the pair, loading the plates you already own.

Get the AdaptaBELL

The Physique in the Headline

Now the photograph at the top of this page.

It belongs to Mock. His company published it, the company’s own version of this story puts a number on it, and we have measured none of that. Judge it the way you would judge any founder’s before and after, which is to say carefully.

What we can say is narrower and more useful. He built his own equipment because nothing on sale would keep getting heavier, and then he trained on it for years rather than weeks. That second part is the one nobody photographs, and a tool with no ceiling is the only kind that lets you do it.

What Everyone Else Made of It

The handles have been on sale long enough to stop being a founder’s story and start being a product other people own.

What $49 Actually Buys

Two handles, four collars, and access to every plate you will ever own. The tool costs less than one month of the gym membership that started this whole story, and the man who drew it did so because he could not find anything worth buying at any price.