Adjustable Dumbbells and Kettlebells
REP x Pépin FAST Series Dumbbells Review: Heavy, Solid, Costly
8.4
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Every product tested at homeNo paid rankings
IronnookSource: repfitness.com
These are the adjustable dumbbells for people who outgrew Bowflex. The all-steel build, the 34 mm knurled handle and the 125 lb ceiling feel like fixed dumbbells, and the lifetime warranty backs that up. They cost $899.99 for the 65 lb pair and $1,499.99 for the full 125 lb set, and the pop-pin changeover is slower than a dial. Heavy lifters should buy them. Anyone who stops at 50 lb should save about $700.
Best for: Strong lifters who want fixed-dumbbell feel up to 125 lb
REP's FAST Series goes up to 125 lb per hand with an all-steel build and a lifetime warranty. At $899.99 to $1,499.99 a pair it is expensive, but nothing else in this class feels as close to fixed dumbbells.
Most adjustable dumbbells stop where strong lifters start. The Bowflex SelectTech 552 ends at 52.5 lb, and PowerBlock's common sets sit well below 100 lb unless you pay for expansion kits. If your dumbbell press is already above that, none of them is a real replacement for a rack of fixed pairs. REP Fitness built the FAST Series for exactly that lifter.
The range is sold in pairs: 65 lb for $899.99, 85 lb for $1,099.99, 105 lb for $1,299.99 and 125 lb for $1,499.99. Those are REP's list prices, and you can step up later with add-on weights, so you do not have to start at the top. The plates are CNC-cut steel with laser-engraved weights, and there is a lifetime warranty on the dumbbells.
That price is a fair argument for buying fixed dumbbells instead. A pair of fixed 100s from a local shop will not match the range, but it will not need a stand either. The adjustable set earns its place if you are short on floor and need many weights, not two or three.
Garage Gym Reviews scored them 4.6 out of 5 and reported a 34 mm handle with a medium knurl, a cradle about 18.9 inches wide and a 125 lb length of about 18.3 inches. The tester dropped them from 10 lb to 125 lb and rated the build 5 out of 5. GearJunkie's review makes the same call on toughness, headlining the all-metal build.
The 552 is still the quickest dial dumbbell to use and the cheapest way to replace 15 pairs, but it asks for trust the brand has not fully earned. The recalled models dropped plates on people, the redesigned Results Series adds metal locking tabs, and the dial housing is still plastic. Buy it on sale, treat it kindly, and never drop it. If you lift heavy or rough, buy a PowerBlock or Nuobell instead.
The S 5100 is the adjustable dumbbell for lifters who miss the feel of a real one. Twist the handle and both ends change in a second, the shape stays compact enough for flyes, and 100 lb a hand covers serious pressing. It costs $999 a pair, the dumbbells are not meant to be dropped and the stand is fussy. Buy it if you lift heavy and have money. Otherwise PowerBlock or Bowflex do the job for less.
The 840 is a convenient bell for beginners and small flats: six weights from 8 to 40 lb in one dial, with a smooth shell and a comfortable handle. It is not a replacement for cast iron. The plates rattle on swings, the body is bulky, 40 lb is a low ceiling, and $149 buys more iron elsewhere.
The handle is the detail that sells it. PowerBlock handles are thick and uncomfortable for some hands, while REP's round, fully knurled bar sits where a fixed dumbbell does. It is also an all-steel design, which is why testers say it feels like one solid object and not a stack of parts.
The sizes jump in 20 lb steps, and the price jumps $200 with each one, so buy for the lifts you do now. Go by your heaviest dumbbell press or row, not your warm-up sets. A lifter who rows 90 lb for sets of ten should look at the 105 lb pair and leave the 125 lb pair for later, since the add-on weights make the upgrade possible without selling the first set.
Each dumbbell starts at 10 lb whichever size you buy, according to Garage Gym Reviews, so a smaller set still covers shoulder raises and curls. The 2.5 lb micro plates help with fine jumps. You are paying for the top of the range, not the bottom, which is why the 65 lb pair is the sensible way in for anyone who is unsure.
Changing weight uses a magnetic pop-pin. You pull the pin, slide it to the plate you want and let the magnet hold it in place. It works, and it is quicker than loading a barbell, but it is slower than turning a dial. Garage Gym Reviews gave the speed 4 out of 5 and said the mechanism "feels like an afterthought". Supersets will have you pausing more than you want.
A pair is also a big object. At 18.3 inches the 125 lb dumbbell is long enough that you need to be careful on overhead presses in a low garage, and the cradle is wide. REP sells a stand for $299.99 and a storage cart for $349.99, which are extra costs on top of an already high price.
If you only need 50 lb or less, the Bowflex in our SelectTech 552 review is about half the cost and faster to change. Our NÜOBELL review covers the other premium option, which tops out at 100 lb with a different dial-based design. PowerBlock's value is in compactness, not in feel.
Buy the FAST Series if you press, row and lunge with 70 lb or more per hand and cannot fit a whole rack of dumbbells. The build is as good as any adjustable on the market, and the warranty means a purchase made now should still be working in a decade.
Skip them if you train at 50 lb or below, or if you only do light accessory work. For those lifters the premium is a lot of money for weight they will not use.