Interface Essential

Business

Images Photography

Money Shopping

Programming

Computer Devices

Phone

Mail

Map Travel

Food Drink

Nature Ecology

Entertainment

Shipping

Culture

Health

Work Education

Artificial Intelligence

Arrows

Streamline 3.0

Ultimate

Core

Flex

Sharp

Plump

Micro

Freehand

Streamline Material

Nova

Cyber

Streamline Vault

Logos

Pixel

Google Material

Tabler

Remix

Feather

Iconoir

Carbon

Solar

Lucide

Brand Logos

Bootstrap

Atlas

Unicons

Ionic Icons

Phosphor

MingCute

Font Awesome

Majesticons

Mynaui

Radix

Heroicons

Flagpack

Outlined Line - Streamline Material Free

Keyboard

Hardware

Rounded Line - Streamline Material Free

Core Remix - Free

Flex Neon - Free

Plump Gradient - Free

Plump Solid - Free

Core Line - Free

Core Solid - Free

Flex Line - Free

Plump Line - Free

Core Line

Plump Line

Core Duo

Sharp Solid

Sharp Line

Flex Solid

Flex Line

Flex Remix

Plump Duo

Plump Solid

Ultimate Regular

Keyboard 2

Keyboard Mouse

Ultimate Bold

Micro Line

Ultimate Duotone

Nova Solid

Ultimate Light

Sharp Duo

Ultimate Colors

Rounded Line - Streamline Material

Ultimate Bold - Free

Computers Devices Electronics

Ultimate Regular - Free

Ultimate Colors - Free

Core Solid

Core Flat - Free

Core Pop - Free

Flex Solid - Free

Plump Flat - Free

Sharp Solid - Free

Plump Remix - Free

Ultimate Light - Free

Outlined Line - Streamline Material

Sharp Line - Streamline Material

Block – Free

Devices

Nova Line

Core Pop

Core Gradient

Core Flat

<p>Flex is all about the curves. Its smooth curves brings fluidity and dynamism to your designs with a modern appeal.&nbsp;The Duo style is perfect for projects that require differentiation between actions, using color to convey meaning effectively. It also allows you to customize the line thickness.&nbsp;All Flex Duo icons are designed on a 14px grid with a 1px default stroke and two customizable colors.</p>

Flex Duo

**Summary**: Flex's two-color system — 1px organic line with dark periwinkle blue primary and lighter blue secondary, adding colour depth and structured hierarchy with the flowing visual quality unique to the Flex family. Organic curves keep the two-color system from reading as corporate despite the blue palette, making it softer and warmer than equivalent duo systems in more geometric families. The tone signals organic structure: "we differentiate through flow, not rigidity." Best for modern SaaS wanting a two-tone icon system with organic visual quality, products with a brand blue where the duo adds depth without imposing rigid geometry, and feature and documentation sections.

**Last updated**: 2026-04-23

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## Fit & Recommendation

### Primary use cases

- Modern SaaS wanting a two-tone icon system with organic visual quality
- Products with a brand blue where the duo treatment adds depth without rigid geometry
- Feature comparison, help, and documentation sections

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## Brand & Cultural Identity

### What it communicates

> "We differentiate through flow, not rigidity."

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## Visual & Technical Specs

### Visual properties

| Property | Value |
|----------|-------|
| Stroke weight | 1px |
| Fill | None (line only) |
| Corner treatment | Smooth fluid curves |
| Color | Dark periwinkle blue + lighter blue secondary |

### Emotional Scores

Flex Duo is somewhat warm — the blue two-color palette is cool, but organic 1px curves soften the coolness compared to geometric duo sets. It is among the softest sub-styles in the catalog — the 1px organic curves in a two-color system remain visually soft despite the structural intent. It is somewhat warm on friendliness — the two-color system adds structure while organic shapes keep it from reading as corporate. It is near neutral on playfulness leaning slightly serious — colour differentiation reads as functional and considered rather than playful or severe. On its human↔mechanical character, it is one of the more human-feeling sub-styles in the catalog — the two-color system adds semantic structure while organic curves retain a natural quality.

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## Pairing & Compatibility

### Typography pairing

- **Primary**: Plus Jakarta Sans — humanist warmth appropriate for the flowing two-color system
- **Alternative**: Outfit — modern humanist, pairs with the blue duo
- **Body**: Inter Regular
- **Avoid**: IBM Plex Sans — engineering register creates personality conflict with organic curves


<p>Flex is a fluid icon family inspired by nature’s curves. It favors smooth, flowing forms. More organic than Core and subtler than the chunky Plump. Read about the <a href="https://blog.streamlinehq.com/flex/" rel="noopener noreferrer" target="_blank">design process</a>.</p>

Fluid icons

Keyboard Lock

Keyboard Lock icon - Flex Duo Set

Download Keyboard Lock SVG vector or transparent PNG icon in Duo, Filled, Stroke style(s) for Sketch and Figma. It belongs to Flex Duo vectors SVG collection.