FLUX.2-klein-base-4B by Black Forest Labs: Open-Weight Model

Runs On

What it takes to serve FLUX.2-klein-base-4B (3.9B parameters): the memory its weights need at each precision, and the cheapest way to rent enough data-center GPUs to hold them.

Precision	Weights	Memory needed	Cheapest setup	Per hour	Also fits
16-bit	7.8 GB	9.3 GB	1x MI300X (192 GB) Vultr	$1.85	1x H100 $1.99 · 1x MI325X $2.00
8-bit	3.9 GB	4.7 GB	1x MI300X (192 GB) Vultr	$1.85	1x H100 $1.99 · 1x MI325X $2.00
4-bit	1.9 GB	2.3 GB	1x MI300X (192 GB) Vultr	$1.85	1x H100 $1.99 · 1x MI325X $2.00

Memory is the weights at that precision plus 20% for the runtime and a short context; a long context needs more. Prices are the lowest on-demand hourly rates in the SAVRN Index, read Sep 18, 2026.

Model Card

By Black Forest Labs, published under apache-2.0, revision a3b4f4849157.

The FLUX.2 [klein] model family are our fastest image models to date. FLUX.2 [klein] unifies generation and editing in a single compact architecture, delivering state-of-the-art quality with end-to-end inference in as low as under a second. Built for applications that require real-time image generation without sacrificing quality, and runs on consumer hardware, with as little as 13GB VRAM.

FLUX.2 [klein] 4B Base is a 4 billion parameter rectified flow transformer capable of generating images from text descriptions and supports multi-reference editing capabilities.

It's a full-capacity foundation model. Undistilled, preserving complete training signal for maximum flexibility. Ideal for fine-tuning, LoRA training, research, and custom pipelines where control matters more than speed. Higher output diversity than the distilled models.

For more information, please read our blog post.

Key Features

Read the full model card (1,325 words)

Identity and Version

Repository: black-forest-labs/FLUX.2-klein-base-4B
Publisher: Black Forest Labs
Task: Image to image
Modality: Image
Library: diffusers
Parameters: 3.9B parameters
Languages: en
Revision: a3b4f4849157f664bdbc776fd7453c2783562f4d
First published: 2026-01-14
Last updated: 2026-02-24

Files and Weights

25 files, 23.7 GB in total. The weights are 5 files totalling 23.7 GB in safetensors.

Weights5 files · 23.7 GB

Configuration9 files · 38.2 KB

Tokenizer4 files · 15.9 MB

Documentation2 files · 19.7 KB

Other4 files · 8.8 MB

Repository1 file · 1.6 KB

Every file

File	Type	Size	SHA-256
flux-2-klein-base-4b.safetensors	Weights	7.8 GB	9c5fed22b76b
text_encoder/model-00001-of-00002.safetensors	Weights	5.0 GB	8c0506e7f493
text_encoder/model-00002-of-00002.safetensors	Weights	3.1 GB	82f2bd839378
transformer/diffusion_pytorch_model.safetensors	Weights	7.8 GB	e109674697ff
vae/diffusion_pytorch_model.safetensors	Weights	168.1 MB	ca70d2202afe
model_index.json	Configuration	422 B	—
scheduler/scheduler_config.json	Configuration	486 B	—
text_encoder/config.json	Configuration	1.5 KB	—
text_encoder/generation_config.json	Configuration	214 B	—
text_encoder/model.safetensors.index.json	Configuration	32.9 KB	—
tokenizer/added_tokens.json	Configuration	707 B	—
tokenizer/special_tokens_map.json	Configuration	613 B	—
transformer/config.json	Configuration	531 B	—
vae/config.json	Configuration	821 B	—
LICENSE.md	Documentation	9.6 KB	—
README.md	Documentation	10.1 KB	—
editing.jpg	Other	2.5 MB	2912ca5a7cb9
others.jpg	Other	3.4 MB	78caed191515
realism.jpg	Other	2.9 MB	6cccc69a683c
tokenizer/chat_template.jinja	Other	4.2 KB	—
.gitattributes	Repository	1.6 KB	—
tokenizer/merges.txt	Tokenizer	1.7 MB	—
tokenizer/tokenizer.json	Tokenizer	11.4 MB	aeb13307a71a
tokenizer/tokenizer_config.json	Tokenizer	5.4 KB	—
tokenizer/vocab.json	Tokenizer	2.8 MB	—

License and Download

License: apache-2.0
Access: Open weights, no gate
Download size: 23.7 GB

Download from Black Forest Labs

Released by Black Forest Labs through its official repository on Hugging Face. Read the license.

Memory Requirements

Precision	Weights in memory
As published	23.7 GB
16-bit	7.8 GB
8-bit	3.9 GB
4-bit	1.9 GB

Weights only, from the published parameter count; the key-value cache and runtime add to this.

Questions About FLUX.2-klein-base-4B

How much GPU memory does FLUX.2-klein-base-4B need?

About 9.3 GB at 16-bit and 2.3 GB at 4-bit: the weights (3.9B parameters) plus a working margin. A long context needs more.

What is the cheapest GPU to run FLUX.2-klein-base-4B on?

At 16-bit, 1x MI300X from $1.85 an hour; at 4-bit, 1x MI300X from $1.85 an hour, at the lowest on-demand prices the SAVRN Index lists.

Can I use FLUX.2-klein-base-4B commercially?

Yes. FLUX.2-klein-base-4B is released under Apache License 2.0. The Apache License 2.0 is a permissive open-source license. It permits commercial use, modification and redistribution. It requires keeping the license and copyright notices and any NOTICE file, stating significant changes, and it includes an express patent grant from contributors.

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