The figure that disqualifies an arm is usually the one at the bottom

A weight rating published as a range is telling you two separate things, and most buyers read only one. A monitor under the stated minimum is outside the specification even though it is nowhere near the ceiling.

That is why these eight arms sort more usefully by their floor than by their headline capacity. The Ergotron HX with the HD Pivot bundle publishes 28–42 lbs (12.7–19.1 kg), the highest floor here. The WorkFit Single HD kit publishes 16–28 lbs and the LX publishes 7.1–24.9 lbs (3.2–11.3 kg). VIVO’s STAND-V100E and Mount-It!’s MI-4881 both publish 4.4–44 lbs, among the widest bands in this set, and HUANUO’s TitanLift publishes 6.61–44 lbs on the RGB version — with the separately sold Non-RGB version rated 6.61–40 lbs, so the variant has to match the figure you checked. HUANUO’s smaller S17 Pro publishes “up to 33 lbs” and no minimum at all.

The practical consequence is that an arm can be wrong for your monitor in two directions. A 24 lb ultrawide clears the HX’s 42 lb ceiling comfortably and still sits 4 lbs below the HD Pivot bundle’s published floor. If the only number you wrote down was 42, you would not have noticed.

Get two figures off your monitor’s spec sheet first

The first is the panel’s own published weight — the figure on the monitor’s spec sheet, not an estimate derived from its diagonal. Screen-size ratings and weight ratings are independent specs here and they do not move together: the HX is rated to ≤49 in and 42 lbs, the LX to ≤34 in and 11.3 kg (24.9 lbs), the WorkFit kit to 30 in and 28 lbs. A panel can pass one of those and fail the other.

The second is the VESA hole spacing, measured rather than assumed. Five of these eight arms publish 75x75mm and 100x100mm and nothing larger. If your monitor uses 200x100mm, exactly one product here publishes support for it: the WorkFit Single HD kit, which also caps at 30 in, so it is not a route to a large curved ultrawide. For 200x200mm you also have the single-arm version of the HX. There is a second kind of gap to watch for: VIVO publishes a 100x100mm maximum for the STAND-V100E without stating a minimum, so a panel with a 75x75mm-only pattern cannot be confirmed compatible from VIVO’s own documents.

Depth is a second weight limit, and almost nobody publishes it

Ergotron’s HX spec sheet is the only document in this set that ties display depth to rated capacity: past 6 in (15 cm) of display depth, capacity is 28 lbs (12.7 kg), and the sheet tells the buyer to check a curved panel’s arc depth against that limit.

That one line changes how you read the rest of the category. It means the HX’s 42 lb ceiling is conditional, and that for a deep curved panel the figure to plan around is 28 lbs. It also means every other arm here that advertises curved compatibility is asking you to trust a named model rather than a measurement. VIVO names the Odyssey G9 in its product title and rates the arm for 49-inch flat or curved screens. Mount-It! marks Odyssey G9 compatibility as yes on its own compatibility field. Neither publishes a depth figure or a curve-radius limit. If your panel is the named model, that is a concrete reference point. If it is a different deep curved monitor, there is nothing published to check it against.

Reach is a desk-depth problem, and three of these arms are silent on it

The comparison that matters is between the arm’s published maximum extension and the distance from your clamp point to where the panel should sit.

The published figures: the Ergotron LX states ≤25.2 in (64 cm), the HUANUO TitanLift states 24.8 in, the HX states ≤23.6 in (59.4 cm), and the S17 Pro states up to 20.89 in. The LX and the TitanLift are within half an inch of each other, so treat them as effectively tied rather than ranked — and note that the LX’s long reach comes attached to a 34 in, 24.9 lb ceiling, which rules it out of the large-ultrawide class entirely.

Two cases need more caution. Mount-It!’s page states 21.3 in in its specifications table and 18 in in its description and structured data for the same arm, without resolving which applies; a 3.3 in discrepancy is enough to decide whether a wide panel centres on a deep desk. And the HX with HD Pivot, the WorkFit kit and the VIVO STAND-V100E publish no extension figure at all. For the VIVO that is particularly awkward, because the arm is marketed for a 49-inch curved panel — the exact case where reach decides whether the setup works.

The desk edge rejects more arms than the weight rating does

An arm that can carry your monitor is still useless if the clamp does not close on your desk. This is where the Ergotron products are weakest on paper: no clamp or grommet thickness range was found for the HX, the HX with HD Pivot, the LX or the WorkFit kit in any document retrieved for this guide. The HX ships with a desk clamp and a grommet mount, so the hardware is there — the range it covers simply is not stated, which leaves anyone with a thick top, a glass top or a sit-stand lip unable to confirm fit in advance.

The four non-Ergotron products do publish ranges, and they differ enough to matter. VIVO’s manual documents a two-position clamp brace: hang it in the upper slots for 3/8–2 in (10–50 mm) desks, or the lower slots for 1.5–3 in (40–80 mm) desks, from the same part. Its grommet route is separately specified for 10–35 mm desks using two 3/8 in (10 mm) holes. HUANUO states 0.8–3.5 in for both clamp and grommet on the TitanLift, and 0.39–3.15 in clamp with 0.39–3.35 in grommet on the S17 Pro.

Two things fall out of those numbers. The clamp range and the grommet range are often different bands, so check the one you actually intend to use — Mount-It!’s grommet range stops at 1.9 in where its clamp goes to 3.3 in. And a floor can exclude you as easily as a ceiling: the TitanLift’s clamp starts at 0.8 in, double the 0.39 in that Mount-It! and the S17 Pro state. If a drawer or a cable tray sits close under your desk edge, the grommet route is the one to plan for, and only four of these eight publish a grommet thickness range.

When a lighter-duty arm is genuinely enough

Three of these products are not large-ultrawide arms and should not be shortlisted as if they were. The LX tops out at 34 in and 11.3 kg (24.9 lbs); the WorkFit Single HD kit at 30 in and 28 lbs; the S17 Pro at 43 in and 33 lbs. No amount of family resemblance to the HX changes the LX’s published ceilings.

Inside their own limits, though, each has something the heavy arms do not. The S17 Pro is the most internally consistent product here: one screen range, one weight cap, one reach figure, tilt from −45° to +90°, and a 20,000 lift-cycle rating. The WorkFit kit exists for a narrow case: a pivot that takes a 200x100mm or 200x200mm pattern.

The heavy-duty group is the VIVO, the Mount-It! and the TitanLift at 44 lbs, plus the two HX configurations at 42 lbs. If your panel’s published weight is over 33 lbs, that group is the whole shortlist.

Reading the durability numbers that are published

Warranty terms here run from Mount-It!’s Lifetime Warranty, through 10 years on the HX, the HX with HD Pivot and the LX, to a 5-year limited term on the WorkFit kit, “up to 5 years” on both HUANUO arms, and 3 years on the VIVO. The qualified phrasing is worth noticing: “up to 5 years” is a weaker commitment than a flat five.

Three products also cite cycle tests, and they are not comparable to each other. Ergotron states that the HX passes its own 10,000-cycle motion test. HUANUO’s TitanLift page cites 50,000+ cycle motion tests, and the S17 Pro is given a 20,000 lift-cycle gas spring rating. Those are three manufacturers describing three different procedures, with no shared method published, so the larger figure is not five times the durability. What the numbers do tell you is which makers were willing to state a figure at all.