TPU hardness explained: 85A vs 90A vs 95A vs 98A vs 72D
- Shore A numbers go up with hardness; 72D is harder than any A grade.
- 95A is the all-rounder and prints on most machines; 85A and 90A need direct drive.
- Only 72D feeds through a Bambu Lab AMS. Print softer grades from the external holder.
- Tensile strength barely changes across the ladder; elongation and stiffness do.
What the number means
Shore hardness is measured by pressing a spring-loaded indenter into the material. The A scale covers soft rubbers; the D scale covers hard plastics. A higher number is harder, and 72D sits above every A grade in stiffness.
Hardness tells you how the part feels and how it prints. It does not tell you strength: every FilamentBay TPU grade tests at around 30 MPa tensile, while elongation falls from over 1100 % at 85A to over 700 % at 72D.
The ladder, by feel
Use the household objects below to pick a grade before you order a sample.
| Grade | Feels like | Bend test | Extruder | AMS |
|---|---|---|---|---|
| 85A | Running-shoe sole | Folds flat, springs back | Direct drive only | No |
| 90A | Bicycle inner tube | Bends easily, firm rebound | Direct drive | No |
| 95A | Shopping-cart wheel | Bends, does not squish | Direct drive or Bowden | No |
| 98A | Tyre tread | Flexes in thin walls | Any | No |
| 72D | Hard hat | Rigid, tough, wear-resistant | Any | Yes |
Which grade for which part
Wearables, cushions and gaskets: 85A. RC tyres, straps and tool grips: 90A. Phone cases, drone bumpers and insoles: 95A. Shoe midsoles and lattice structures: 98A. Saddles, wheels and housings that get scraped: 72D.
When in doubt start at 95A. It is the fastest to print, forgives Bowden extruders at low speed and still feels unmistakably rubbery.
