PROIRON Cast Iron Adjustable Dumbbell Set Review

The PROIRON in 60 seconds

The PROIRON cast iron dumbbell sets are the cheapest way to start strength training at home. At around £100 for the 20kg set or £120 for the 30kg set, you get cast iron plates, chrome spinlock bars, and a barbell connector tube -all for less than a single MuscleSquad dumbbell.

The trade-off is everything that makes selectorised dumbbells convenient. Weight changes take 30-60 seconds of unscrewing collars and swapping plates. The spinlock collars loosen during use. And the max weight will be outgrown by most consistent trainers within a year.

Which set should you buy?

Who makes PROIRON?

PROIRON is a brand of Shanxi Regent Works Inc., a Chinese manufacturer founded in 1997 in Taiyuan, China. They registered the PROIRON brand worldwide in 2009 and have become one of the bestselling dumbbell brands on Amazon across the UK, Germany, France, and Italy. They know how to make cast iron fitness equipment at scale.

What you get in the box

Both sets include:

• Cast iron plates (0.5kg, 1.25kg, and 2.5kg denominations)
• 2x 35cm chrome-plated dumbbell bars with 143mm knurled grip
• 4x spinlock collars with rubber O-ring design
• 1x connection steel tube (converts to a barbell)

The 30kg set includes the same plate types as the 20kg, plus 8 additional 2.5kg plates. The barbell connector is a genuine bonus -it lets you do barbell exercises (curls, overhead press, rows) with the same plates. At this price, getting both dumbbell and barbell capability is impressive.

The spinlock problem (both sets)

This is the fundamental limitation of spinlock dumbbells, not just PROIRON's. You unscrew the collar, remove or add plates, then screw it back on. Every. Single. Weight change.

PROIRON uses a rubber O-ring design that's meant to keep the collars from loosening. In practice, it helps but doesn't solve the problem entirely -"spinlocks loosen during use" is the single most common complaint across Amazon UK reviews for both sets.

This means:

• No supersets -you can't switch weights fast enough
• No drop sets -same problem
• Safety concern -check collar tightness between sets
• Workout flow killed -rest periods become plate-changing sessions

The weight ceiling problem

Even the 30kg set gives you only 15kg per dumbbell. Consider how fast you'll hit that ceiling:

• A goblet squat at 15kg is a warm-up for most people after 3-4 months
• Dumbbell rows at 15kg will be too light within weeks for anyone with a baseline of fitness
• Even bicep curls at 15kg becomes achievable fairly quickly for most men

You can buy additional standard 1-inch plates to add more weight, but the bars are only 35cm long, limiting how many plates you can stack.

Quality concerns

One Amazon reviewer who reordered after several years reported a decline in manufacturing quality -newer dumbbells were "warm to the touch instead of cold steel," approximately 200g lighter each, and had "rougher finishing on the lock nuts." This suggests possible changes in materials or manufacturing standards over time. Worth keeping in mind, though most reviews remain positive.

The real question: PROIRON vs saving up

Here's the honest maths. If you buy the PROIRON 30kg set for £120 and outgrow it in 6-12 months, you'll then need to buy something else. A MuscleSquad (32.5kg model) at ~£210 brings your total to £330. If you'd saved for 2-3 months longer and bought the MuscleSquad directly, you'd have spent £210 total and had a better product from day one.

The PROIRON does retain some resale value on Facebook Marketplace and Gumtree (cast iron holds its value), so factor that in. But the principle stands: buying cheap often means buying twice.

Who are these for?