TPU shore hardness explained
Every TPU spool lists a number like 95A or 85A. That is its shore hardness, and it is the single most useful spec for choosing a flexible filament. It tells you how soft the printed part will feel and, just as important, how hard the filament will be to print. This guide explains the scale, compares the common grades and matches each one to the parts it suits.
What shore A hardness means
Shore hardness is measured with a durometer, a gauge that presses a spring loaded steel pin into the material and reads how far it sinks in. The test is standardized in ASTM D2240 and ISO 48-4. Each shore scale runs from 0 to 100, and a higher number means a harder material.
There are several scales for different kinds of material. The A scale is the one used for soft rubbers and elastomers, which is why TPU grades end in "A". Harder plastics are measured on the D scale, so you will occasionally see a very stiff flexible filament rated in D instead.
Lower number, softer part
An 85A TPU is noticeably softer and stretchier than a 95A TPU. The difference of 10 points sounds small, but in the hand and at the printer it is large.
Common TPU grades
Most TPU filament sold for desktop printers falls between roughly 85A and 98A. When a listing just says "TPU" with no number, it is usually 95A, the grade most brands treat as their default because it balances flexibility with easy printing.
| Grade | Feel | Printability | Good for |
|---|---|---|---|
| 85A | Soft and rubbery, easy to squeeze | Hard; direct drive and slow speeds | Gaskets, seals, soft grips, wearables |
| 90A | Soft but springy | Moderate; direct drive recommended | Grips, dampers, straps, gaskets |
| 95A | Firm, bends with effort | Easiest; the common default | Phone cases, bumpers, wheels, feet |
| 98A | Stiff, slight give | Easy; closest to rigid filament | Tough wheels, rollers, impact parts |
Softer specialty grades exist too, such as NinjaTek's NinjaFlex Edge at 83A, but they are the hardest of all to print and many printers do not officially support them. Bambu Lab, for example, states that its printers do not currently support TPU rated below 85A.
How hardness affects printing
The softer the TPU, the more it behaves like a wet noodle in the extruder. Soft filament compresses and buckles when the drive gears push it, especially if it has to travel through a long tube first. That is why printability drops as the number goes down.
Extruder type
A direct drive extruder, with the drive gears right above the hotend, is strongly recommended for anything softer than 95A. Many 95A filaments can be printed on a Bowden setup with care, and some feed better than most: NinjaTek designs Cheetah to print on Bowden machines, and Polymaker says its PolyFlex TPU95-HF can also run on a Bowden setup.
Speed
Softer grades need slower printing. As a rough guide, 95A often prints well at around 25 to 40 mm/s on a direct drive machine, while 85A may need 15 to 20 mm/s or less. Keep retraction short or turn it off, since pulling soft filament back and forth invites jams.
Nozzle size and multi material systems
Very soft TPU can struggle through small nozzles. Bambu Lab recommends 0.6 or 0.8 mm nozzles for its 85A TPU, does not support it on a 0.4 mm nozzle, and does not support it in the AMS, AMS lite or AMS 2 Pro. The AMS HT can hold it, but only as a sealed enclosure feeding through a dedicated TPU outlet. Automatic filament changers generally need harder grades, so check your system's compatibility list before buying a soft spool.
For full print settings, drying and troubleshooting, see the TPU filament guide. TPU absorbs moisture readily, so dry it before printing whichever grade you choose.
Which hardness to choose
Phone cases and protective covers
95A is the usual pick. It holds its shape around the device and absorbs drops, while still printing easily. Go softer only if you want a very grippy, squishy case.
Gaskets and seals
85A to 90A compresses more easily and conforms to the mating surface, which is what a seal needs.
Wheels, tires and feet
95A for most wheels and rubber feet. 98A for wheels that carry load and need to keep their shape under weight.
Grips and wearables
85A to 90A feels soft and comfortable on handles, straps and watch bands. If your printer struggles with soft TPU, 95A still works as a firmer grip.
Not sure you need a flexible filament at all? The PLA vs TPU comparison covers when a rigid material is the better call.
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Compare live TPU listings by brand, weight and price per kg. Check the shore hardness in each listing so you buy the grade your project and printer need.
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