Polymer vs aluminium: which backpack material is right for you?
SOLID GRAY® makes hard shell backpacks in two primary materials: polymer and aluminium composite. The silhouette is the same. The construction method is the same. But the material choice creates meaningful differences in weight, appearance, feel, and price. Here is an honest comparison.
How both are made
Both the Polymer and Aluminium hard shell backpacks are produced using the same CNC-based manufacturing process. A large sheet of material is milled into shape, folded into a structural form, and assembled by hand from over 100 individual parts. The result is a rigid, geometric shell with the same iconic SOLID GRAY® silhouette.
The Aluminium shell uses an aluminium-polymer composite: a core of polymer plastic with thin aluminium layers on both sides. Because of this construction, both sides of the sheet need to be precision-milled before the shell can be folded and assembled. The result is a material that combines the visual and tactile qualities of real aluminium with a refined structural core.
The Polymer Hard Shell
The Polymer Hard Shell uses a custom-engineered polymer plastic with a matte finish. It is the original SOLID GRAY® model, introduced in 2012, and remains the most widely used.
Weight. 1.2 kg. Comparable to or lighter than many fabric backpacks of similar volume.
Appearance. Matte, clean, geometric. Available in Bold Red, Crisp White, Stealthy Black, and Supreme Blue. The surface has a consistent, restrained finish that reads as design-led without being aggressive.
Feel. The back panel has a degree of flex, allowing natural movement during wear. The exterior is firm but not completely rigid in every direction.
Durability. The polymer shell holds up extremely well to daily use. Surface scratches can appear from sharp objects over time but do not affect structural integrity. Multiple customers have used the same backpack daily for 10 or more years.
Price. USD 259 / EUR 235. The most accessible entry point into the SOLID GRAY® range.
Best for. Daily commuting, cycling, travel, and anyone who wants the full SOLID GRAY® experience at the most accessible price point.
The Aluminium Hard Shell
The Aluminium Hard Shell uses an aluminium-polymer composite sheet, CNC-milled on both sides and folded into the same structural form as the Polymer. The result is a backpack with an unmistakably metallic appearance and a different tactile quality.
Weight. 1.3 kg. A fraction heavier than the Polymer, but still within the range of a comfortable daily carry.
Appearance. Metallic, industrial, immediately striking. The aluminium surface catches light differently than polymer, creating a more dynamic visual presence. A coated finish keeps the surface durable and consistently lustrous over time without developing a patina.
Feel. The back panel is firmer than the Polymer version and comes with back padding included as standard. The exterior has the distinctive hardness and cool surface temperature of real metal.
Durability. The aluminium composite shell and its protective coating hold up well to daily use, maintaining their appearance over time.
Price. USD 688 / EUR 689. A significant investment, positioned as a premium and collectible object as much as a functional backpack.
Best for. People who want the most visually striking version of the SOLID GRAY® design, collectors, and anyone who sees their backpack as an investment piece or statement object.
Side by side
| Polymer | Aluminium | |
|---|---|---|
| Weight | 1.2 kg | 1.3 kg |
| Shell material | Custom polymer plastic | Aluminium-polymer composite |
| Back panel | Flexible | Firm, padding included |
| Surface finish | Matte | Coated metallic |
| Colors | 4 shell colors | Metallic finish |
| Price | USD 259 / EUR 235 | USD 688 / EUR 689 |
| Best for | Daily use, commuting | Statement piece, collectors |
Which should you choose?
Choose the Polymer if:
You want the most versatile daily option, are new to hard shell backpacks, commute regularly, or want the full SOLID GRAY® experience at the most accessible price. The Polymer is the backpack most SOLID GRAY® customers use every day.
Choose the Aluminium if:
You want the most visually striking version, value the premium material and the industrial aesthetic, or are looking for something that functions as both a daily bag and a collectible design object. Several customers own both and use the Polymer for daily commuting and the Aluminium for travel or occasions where visual impact matters more.
If you are unsure:
Start with the Polymer. It is the original model, the most tested, and the one with the longest track record. If the SOLID GRAY® design appeals to you in polymer, the aluminium version will appeal to you more.
What both have in common
Both models share the same iconic silhouette, the same interchangeable strap system, the same internal structure, and full compatibility with all SOLID GRAY® accessories. Both are handmade in Amsterdam in small batches. Both are backed by the Lifetime Crash Service and last for decades with normal use.
The choice between polymer and aluminium is ultimately about aesthetic preference and how you relate to your backpack. Both are strong choices.
More from SOLID GRAY®:
- What is a hard shell backpack?
- Are hard shell backpacks practical for daily use?
- Are hard shell backpacks comfortable?
- Hard shell vs soft backpack: what is the difference?
- What is a futuristic backpack?
- Why are premium backpacks more expensive?
- Can a backpack be both a design object and a daily bag?
- About our products