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  • 75,000+ Customers

  • 1,800+ Trustpilot reviews

  • Elite 2-Year Warranty
Customers rate us 4.9/5 based on 3070 reviews.

40kg SmartBells® Twist Adjustable Dumbbells

€417,95
  • Easily shift from 5kg to 40kg
  • Pair of 17-in-1 Adjustable Dumbbells
  • Push down and turn the dial to change the weight
  • Fast weight changes without breaking your workout
  • Quality checked and come with 24 Months Warranty
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🚚 FREE avg next day delivery
🛡️ 2-YEAR warranty on all dumbbells
😊 Over 75,000+ happy customers

Free & Next Day UK Delivery

We offer FREE NEXT DAY Delivery to England, Scotland & Wales on ALL orders. All other orders will be subject to small additional delivery charges.

Why choose BRAINGAIN
  • Rated Excellent on Trustpilot, over 1000 5* reviews!
  • Over 50,000 Adjustable Dumbbells sold.
  • UK’s leading Fitness & Home Gym Brand.
  • Spread the cost with Klarna or Clearpay.
  • 2 Years Warranty on everything.

Overview

Our SmartBells™ 40kg are dial-adjustable dumbbells that replace a full rack. One compact pair covers 5kg to 40kg across 17 precise settings.

Simply push down and turn the dial to select your weight in seconds, giving you total control over your training without breaking your rhythm.

Built with durable steel plates and a knurled handle for a secure, comfortable grip, with a steel base tray for stability at rest. Designed for lifters who want to Train Smarter.

Features

5kg–40kg in 17 settings: precise weight steps for controlled progression. Weight settings include: 5kg, 7kg, 9kg, 11kg, 13kg, 15kg, 18kg, 20kg, 22kg, 25kg, 27kg, 29kg, 32kg, 34kg, 36kg, 38kg, 40kg.

Equivalent to 17 dumbbells per pair: full rack capability without the space requirement.

Dial adjustment (push down to turn): change weights in seconds without interrupting your workout.

Integrated safety-lock system: only the selected weight is engaged for secure lifting.

Steel plate construction: durable design built for long-term use.

Knurled handle: secure grip with a balanced, comfortable feel.

Steel base tray: stable foundation and tidy storage.

Warranty

All of our products come with a 24 month warranty as standard. We offer extended warranty options on selected products which if available will be shown above the 'Add to Cart' button above.

  • Turn of a dial

    Easily shift from 5kg to 40kg with the innovative BRAINGAIN 40kg Adjustable Dumbbells. No more need for 17 seperate weights.

  • Base or Stand

    The 40kg Adjustable Dumbbells come with their own tray to facilitate simple weight changes and tidy storage. Separate stands can be purchased to bring the adjustable dumbbells up to waist height.

  • Total Body Workouts

    Adjustable Dumbbells can be used for all your home workout needs and exercises including presses, swings, deadlifts, squats, curls, sit-ups, snatch, renegade row, twists, clean & press, thrust and more.

By the Numbers

34
dumbbells in one pair
17
weight settings
5-40kg
per dumbbell
4.9/5
from 3000+ reviews

Your Body Is Already Losing Muscle

From age 30, your body naturally loses muscle mass. Without resistance training, it only gets worse.

3-5%

muscle mass lost per decade from age 30. After 50, this accelerates to 1-2% per year.1

10-17%

lower risk of all-cause mortality, cardiovascular disease and diabetes from strength training.2

30-60 min

per week is the optimal dose - just 3x 20-minute sessions for maximum longevity benefit.3

1 Source 2 Source 3 Source

Built Different. Here's the Proof.

We surveyed 659 BrainGain customers across 5 key markets.

90%

said the value justified the price or price wasn't even a concern.*

72%

train 3 or more times per week with their BrainGain dumbbells.*

81%

want to buy more BrainGain products (accessories, supplements, training).*

* Source: BrainGain Customer Survey, February 2026, n=659 across 5 markets.


Rated Excellent on Trustpilot

Don't just take our word for it. Over 1,800 verified reviews from real customers.

★★★★★

Really Happy!

Dean Moran

Really happy with these adjustable weights, easy to put together and smoothly changes weights from 2.5kg all the way up to 40kg.

★★★★★

I previously was using the 24kg

Lee Philpott

I previously was using the 24kg dumbells which are still going strong but have upgraded to the 40kg octagon dumbells, good quality dumbells and look amazing.

★★★★★

Great Quality 40kg Dumbbells

Stephen Hammond

They are great quality and very between 2.5 to 40kg. Perfect for my home gym setup. Quality and ease of use is 10/10 saves so much space and work really well for both me and my girlfriend.

TrustPilot Read all reviews →
40kg SmartBells dimensions: 47.5 x 25 x 25 cm

DIMENSIONS

Length: 47.5cm

Height: 25cm

Width: 25cm

Handle Length: 10.2cm

Handle Diameter: 3.85cm

"Game-Changer for Home Workouts!"

These adjustable dumbbells are a fantastic addition to my home gym. The Smart Click technology makes switching weights super easy, and the stand keeps everything neat and accessible. Highly recommend!

Liam Stafford - Manchester

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    Product Highlights

    Explore the key features of our 40kg SmartBells® Twist Adjustable Dumbbells by clicking on the pulsing highlights.

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    Us vs. Them

    Not overhyped or overpriced.
    Just premium adjustable dumbbells built to last.

    BrainGain
    Generic Adjustable
    Gym / Fixed Weights
    Max weight
    Up to 40kg
    24-40kg
    Depends on gym
    Weight settings
    17 per dumbbell
    8-12
    Fixed
    Change weight in 1 sec
    No rattle during lifts
    Replaces entire rack
    2 year warranty
    Premium support