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FLUX.2 Flexvs.FLUX.2 Klein 4B

Which one is better?

In our own test both are on par. FLUX.2 Klein 4B has no arena rating yet. FLUX.2 Klein 4B has no API price.

Same prompt, two images

Same task, the first image of each. The task with the biggest difference is preselected.

FLUX.2 Flex: Typography and layout, first image from the fixed test run
FLUX.2 Flex71 out of 100
FLUX.2 Klein 4B: Typography and layout, first image from the fixed test run
FLUX.2 Klein 4B21 out of 100

Result for “Typography and layout”:FLUX.2 Flex ahead

Prompt given to both modelsCreate a square editorial poster for an imaginary night train called MONDFALTER. Show the exact German headline MONDFALTER and the exact subline BERLIN NACH LISSABON. Use a restrained midnight-blue and warm-cream palette, one stylized moth, strong Swiss-grid typography, generous negative space, and no additional words or logos.

What the rating looks at: Legible text, hierarchy, and composition.

“Ahead”: better in all three rating rounds. “Slightly ahead”: a higher value, but not in every round.

Test protocol of the images

Both models receive the same archived prompt in exactly one request, and the first result counts. Files are normalized to 1,024 × 1,024 pixels without cropping. Provider resolution, randomness, quality tier and prompt processing can still differ. The images are a practical visual test, not a reconstruction of the arena configuration.

Character and detail

FLUX.2 Flex: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:25 PM. Source

FLUX.2 Klein 4B: fal, requested 1024x1024, n=1, seed=707400387, Fal's published 4B text-to-image endpoint; default four inference steps, estimated cost $0.005000, generated Nov 1, 2026, 9:01 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: 985a75b38642a9f0e5e0c0e0c67f1b7f67780d42bd2168fa24e9a7a7a94b0da6

FLUX.2 Flex image SHA 256: 43b43d5782192d7284de2b824dd1caaaa6b25032d22fc3f8565d438b137089f3

FLUX.2 Klein 4B image SHA 256: 170cebb7cf75bc033a92371199812674f9cfa9641d5e9fb13947ccf892d4ed53

Infographic

FLUX.2 Flex: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:25 PM. Source

FLUX.2 Klein 4B: fal, requested 1024x1024, n=1, seed=290140178, Fal's published 4B text-to-image endpoint; default four inference steps, estimated cost $0.005000, generated Nov 1, 2026, 9:01 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: ed65cb4e6a51e2336f8b149ad4cbb16e020f07d527ad94362e719d2dcf91d94f

FLUX.2 Flex image SHA 256: 105f60cdeb71a27021ffff1ad3c0ad919df4e5c74ad83b4628fbd64a8d795a09

FLUX.2 Klein 4B image SHA 256: 42b729a5a72207b5a92464f3ecf1713459ab1b105c3041c14b75c7622630015e

Product photography

FLUX.2 Flex: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:25 PM. Source

FLUX.2 Klein 4B: fal, requested 1024x1024, n=1, seed=1254275381, Fal's published 4B text-to-image endpoint; default four inference steps, estimated cost $0.005000, generated Nov 1, 2026, 9:00 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: c67fd71e91304458a2feef5c91efa8677260fab0c0099a29a2c52cb579f5b2f3

FLUX.2 Flex image SHA 256: 9fef39b1500635ddbf78bcb8d3d9a68463ce952aa1fab89d12f6efe023907de7

FLUX.2 Klein 4B image SHA 256: 8fae4a7f6abb7467281c439dc93aa656031626f88c8a54f95f49850cbf045580

Typography and layout

FLUX.2 Flex: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 2:01 PM. Source

FLUX.2 Klein 4B: fal, requested 1024x1024, n=1, seed=1270698692, Fal's published 4B text-to-image endpoint; default four inference steps, estimated cost $0.005000, generated Nov 1, 2026, 9:00 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: 2e012c3d14ee5dd02203a94f394ca80a5038cdebd6032b25a8b8a221f2255419

FLUX.2 Flex image SHA 256: 324f87bf898593446a400abb43bd00eee015fa0a1dc160db0f864402fc0b38af

FLUX.2 Klein 4B image SHA 256: 7c2c3e30c20c98e90033087b2b95b151bddc3252dd4aed7092fcbca4ae4ea96e

The numbers at a glance

Arena ratingfrom votes by users · higher is better
1,156

FLUX.2 Flex

Rank 17 of 22

n/a

FLUX.2 Klein 4B

not in the arena

GraduallyBenchour own rating, 0 to 100 · higher is better
57

FLUX.2 Flex

Rank 35 of 74

37

FLUX.2 Klein 4B

Rank 55 of 74

Price per imagedollars through the API · lower is better
$0.06

FLUX.2 Flex

fairly cheap

n/a

FLUX.2 Klein 4B

no API price

Ranks among the 22 image models with an arena rating and the 74 with a GraduallyBench run; prices compared with 28 models with an API price.

FLUX.2 Flex

Subscription
No Black Forest Labs subscription includes this model. Through other providers from €6.83 a month (Poe Basic, with limited points). 26 plans in Germany.
Via API
$0.06 per image, 100 images $6.

FLUX.2 Klein 4B

Subscription
No Black Forest Labs subscription includes this model. Through other providers from €6.83 a month (Poe Basic, with limited points). 12 plans in Germany.
Via API
No API price known. Access: API, local.
License
Open weights.

Subscriptions only count plans that name exactly this model. Subscription prices include VAT, API prices are in dollars.

Arena rating (LMArena) from Oct 28, 2026 · GraduallyBench from Nov 1, 2026 · API prices from Oct 28, 2026 · Subscription database from Sep 29, 2026 (34 days old)

All data side by side

The better value is bold. For ratings only when the gap is clear.

KennzahlFLUX.2 FlexFLUX.2 Klein 4B
Ratings
Arena ratingfrom votes by users, higher is better1,156n/a
Arena rankRank 17 of 22n/a
Arena votesmore votes, a safer rating156,876n/a
GraduallyBenchour own rating, 0 to 1005737
GraduallyBench by task
Typography and layoutLegible text, hierarchy, and composition7121
Product photographyMaterials, reflections, and fine details5654
Character and detailAnatomy, clothing, and spatial consistency5853
InfographicNumbers, labels, and visual organization4119
API price
Per imagelower is better$0.06n/a
100 images$6n/a
Profile
ReleasedNovember 2025n/a
Weightsopen means: runs locallyproprietaryopen
AccessAPI, Web appAPI, local
Parametersnot published4 billion
Largest output4 Megapixelnot consistently published
Plans in Germanynaming exactly this model2612

API prices for one image at 1,024 × 1,024 pixels according to Artificial Analysis.

Sources: FLUX.2 Flex model source (verified Sep 24, 2026) · FLUX.2 Klein 4B model source (verified Nov 1, 2026)

Arena ratings by category

From blind votes on LMArena. “Ahead” means the lead is clear.

No shared arena score in the stored snapshot

The stored benchmark database contains no measurement for FLUX.2 Flex and FLUX.2 Klein 4B from the same arena and category. Older model versions are not used as substitutes.

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