The BowFlex SelectTech 840 Adjustable Kettlebell is a good buy when your kettlebell loads land on its six settings (8, 12, 20, 25, 35, and 40 pounds) and one bell at a time is all you need. This BowFlex SelectTech 840 review focuses on what the “replaces six kettlebells” line leaves out: the size of each jump between settings. Two of those jumps, 12 to 20 pounds and 25 to 35 pounds, are big enough to decide the purchase on their own.
If your plan lives inside those gaps, or you need two bells at the same moment, a single cast-iron kettlebell at your working weight or a pair of adjustable dumbbells will fit better. Both alternatives appear in the last section before the sources.
Bottom line
The 840 turns a row of six kettlebells into one dial-set bell with a single storage spot, which is a real advantage in a small room. BowFlex still lists it under the SelectTech 840 name as model 100790, and the recall search compiled for this review surfaced no recall naming it.
Its limits are arithmetic, not mystery. The settings climb in uneven steps, the top setting is 40 pounds, and only one setting exists at a time. Map your own loads against the ladder below before buying; if most of them land on or near a setting, the 840 fits.
Identity lines on the 840 listing
| Listing line | Stated value | What it decides |
|---|---|---|
| Name | BowFlex SelectTech 840 Adjustable Kettlebell | BowFlex moved some dumbbells to “Results Series” names; the kettlebell still carries the SelectTech 840 name |
| Model number | 100790 | Match it on the listing, the box, and any warranty registration |
| Settings | 8, 12, 20, 25, 35, and 40 lb | Your loads must fit these six numbers |
| Adjustment | Dial selection | Follow the manual’s sequence for every change |
| Construction | Plastic outer shell over a dial-selected weight system | Handling, drop care, and cleaning differ from cast iron |
| Manual | SelectTech 840 owner’s manual from BowFlex | Permitted uses and care instructions |
BowFlex describes the 840 as replacing up to six kettlebells. The rest of this review tests what that means in practice.
The setting-ladder gap table
Here are the six settings as steps, with the added load and the jump as a percentage of the setting you are leaving. Kilogram figures are converted at 1 lb = 0.4536 kg and rounded to one decimal.
| Step | From → to | Added | Jump | In kilograms |
|---|---|---|---|---|
| 1 | 8 → 12 lb | 4 lb | 50% | 3.6 → 5.4 kg |
| 2 | 12 → 20 lb | 8 lb | 67% | 5.4 → 9.1 kg |
| 3 | 20 → 25 lb | 5 lb | 25% | 9.1 → 11.3 kg |
| 4 | 25 → 35 lb | 10 lb | 40% | 11.3 → 15.9 kg |
| 5 | 35 → 40 lb | 5 lb | 14% | 15.9 → 18.1 kg |
The percentage is the added load divided by the starting setting: 8 ÷ 12 = 0.67 for step 2, and 10 ÷ 25 = 0.40 for step 4. Those two steps are the gaps that matter. Whether a gap is acceptable is a question for your plan and coach; the table only shows where the gaps are.
Map your own loads. Kettlebell plans are often written in kilograms, so convert and compare. These are illustrative loads, not recommendations:
- 16 kg is 35.3 lb. The 35 lb setting is within 0.3 lb, a near-exact match.
- 12 kg is 26.5 lb. It sits in the 25-to-35 gap; the nearest setting, 25 lb, is 1.5 lb light.
- 8 kg is 17.6 lb. It sits in the 12-to-20 gap: 20 lb is 2.4 lb heavy, and 12 lb is 5.6 lb light.
- 20 kg is 44.1 lb and 24 kg is 52.9 lb. Both are above the 840’s 40 lb top setting.
Write every kettlebell exercise in your plan with its load, then mark each one as on a setting, within a pound or two, in a gap, or above 40 lb. If the “in a gap” and “above 40” rows hold the exercises you do most, the 840 is the wrong tool, however convenient the dial is.
The next-step test. Suppose (illustrative) your current load for an exercise is 12 lb and your plan calls for progressing it. The 840’s next setting is 20 lb, 67% heavier, with nothing in between. At 25 lb, the next step is 35 lb, 40% heavier. A fixed-bell collection can fill those gaps with intermediate bells; the 840 cannot.
“Replaces six kettlebells” means one at a time
The six settings add up to 8 + 12 + 20 + 25 + 35 + 40 = 140 pounds of fixed bells that the 840 stands in for. That is the storage win: one footprint instead of six bells on the floor or a rack.
It is also the limit. Only one setting exists at a time, so the 840 cannot supply two bells for double-kettlebell exercises, two people training at once, or a circuit that alternates loads without stopping to change the dial. Each change is a pause in the session. If your sessions use one load per exercise and rest between sets, that pause costs little; if they alternate loads constantly, it adds up.
One body at every setting
Because the 840 changes load by locking selected weight into one body, its outer size is not expected to shrink at the light settings the way a small fixed bell does. Treat the 8 lb setting as having roughly the same outer shape as the 40 lb setting, and confirm that against the listed dimensions. For someone who mostly uses the lightest settings, that is worth weighing against a small cast-iron bell. Check the listed dimensions against your hands and the movements you plan, especially anything where the bell rests against your forearm.
Recall and identity checks
BowFlex keeps a product recalls page and a separate dumbbell recall information page, and the Consumer Product Safety Commission has published a recall notice for Bowflex SelectTech barbells. The recall search compiled for this review on September 29, 2026 surfaced none of those naming the 840.
The site’s BowFlex SelectTech 52 review explains how older SelectTech dumbbell models were named in a recall and why similar names are not proof of identity. Apply the same habit here: confirm “SelectTech 840” and model 100790 on the listing and the box, and check BowFlex’s recall page and CPSC with your serial number, especially when buying used.
Floor, storage, and care
Treat the dial mechanism as a mechanism. Set the kettlebell down under control and follow the manual’s handling and care instructions rather than cast-iron habits. A mat gives it a consistent landing spot; the site’s roundup of exercise mats for garage floor workouts covers the options.
Wipe it down after sweaty sessions. The cleaning principles in the site’s guide to cleaning adjustable dumbbells between workouts apply to selector equipment generally: keep moisture and grit away from the selection mechanism and follow the maker’s cleaning instructions.
Who should buy it
- Your planned kettlebell loads land on or within a pound or two of 8, 12, 20, 25, 35, or 40 lb.
- You train with one bell at a time and rest between sets.
- Floor space for a row of fixed bells is the problem you are solving.
- You will follow the manual’s handling and care instructions.
Who should skip it
- Your plan relies on loads in the 12-to-20 or 25-to-35 lb gaps.
- You need two bells at once, or two people train together.
- You already need more than 40 lb for your main movements.
- You mostly use the lightest settings and want a physically small bell.
For a pin-select alternative, the PowerBlock 18–35 lb review maps a different four-setting ladder. Its 26-to-35 lb step deserves the same planned-load check; switching mechanisms does not remove missing intermediate weights.
Practical alternatives
If your plan uses one or two loads, a single cast-iron bell at each working weight is simpler: no dial, no mechanism, and a smaller body at light weights. The site’s roundup of kettlebells for a home gym compares options, and the budget versus premium kettlebells comparison shows which documented differences are worth paying for.
If you need finer steps or two implements at once, adjustable dumbbells can answer both problems. The site’s garage-gym adjustable dumbbell fit map compares several systems by their weight steps.
Sources consulted
- BowFlex SelectTech 840 Adjustable Kettlebell product page
- BowFlex SelectTech 840 owner’s manual
- BowFlex product recalls page
- CPSC recall notice for Bowflex SelectTech barbells
- Garage Gym Reviews SelectTech 840 review
- BarBend SelectTech 840 review
Specifications and product identities were compiled through web search on September 29, 2026 and should be confirmed on the seller’s page for your exact size, color, and version. This is researched fit analysis without hands-on testing.
FAQ
What weights does the BowFlex SelectTech 840 have?
Six settings of 8, 12, 20, 25, 35, and 40 pounds, chosen with a dial. In kilograms that is roughly 3.6 to 18.1.
Does the SelectTech 840 replace a set of kettlebells?
It replaces six fixed weights one at a time. It cannot give you two bells at once, and the six bells it stands in for would total 140 pounds of separate kettlebells.
Has the BowFlex SelectTech 840 been recalled?
The recall search compiled for this review on September 29, 2026 surfaced BowFlex’s recall pages and a CPSC recall of SelectTech barbells, but no recall naming the 840. Check BowFlex’s recall page and CPSC with your model number before buying.
What is the model number of the BowFlex SelectTech 840?
BowFlex lists the SelectTech 840 Adjustable Kettlebell as model 100790. Match that number on the listing and on the box.