Siraya Tech Flex TPU 85A vs NinjaTek NinjaFlex 85A

Who this comparison is for

This page is for anyone choosing between these two specific spools: Siraya Tech Flex TPU 85A in Black (1 kg) and NinjaTek NinjaFlex 85A in Midnight Black (1 kg). At 85A, both are softer than the common 95A grade, which makes them harder to push through a feed path. So the questions are mostly about your printer: how it feeds filament, how fast you want to print, and how you'll keep the spool dry. If you're not sure what 85A means in practice, start with our TPU hardness guide. For other brands and grades, see the TPU filament shortlist.

How we compared them

This is a research-based comparison. Every figure below comes from the makers' own data sheets, product pages, and guides, listed in the sources, plus Bambu Lab's published AMS rules. We haven't tested either filament, so nothing here is a measured result of ours. Where a maker describes its own product, such as "Up to 5x speed" or "Abrasion resistance 20% better than ABS," we label it as the maker's claim.

We only put test figures side by side where both makers name the same test standard. For these two, that covers four figures, all ASTM methods, and we explain below what each maker says about how its samples were made.

Side-by-side specs

Speed: different guidance, not a race

This is the clearest difference in intent. Siraya describes Flex TPU 85A as a "high-flow formulation" that "can be printed at speeds between 30 and 90 mm/s," and advises starting at the low end and working up. Its product page also claims it prints "up to 5 times faster than comparable TPU filaments" and quicker than "typical TPU 95a." That's Siraya's claim, with no test method or comparison filament named on the pages we checked.

NinjaTek's guidance for NinjaFlex is much slower: 10–20 mm/s for top and bottom layers and 15–35 mm/s for infill. Its troubleshooting guide suggests lowering speed further, in 2 mm/s steps, for some problems, and keeping NinjaFlex infill at 20% or more, because flexible filaments "often require more infill than their more rigid counterparts."

Siraya gives one range and NinjaTek gives speeds per feature, so these aren't the same measure. Read them as each maker's starting advice for its own filament, not as a measured result.

Temperatures and build plates

The nozzle ranges meet at one point, 225 °C. Siraya's range is 200–225 °C, and it says printers with shorter melt zones may suit the higher end (215–225 °C) and those with longer melt zones the lower end (200–210 °C). It adds that the black version "often performs better at slightly cooler temperatures" than the white. NinjaTek's range is 225–250 °C. So switching from one to the other likely means changing your nozzle temperature, not just loading a new spool.

The beds are closer. Siraya gives 20–50 °C on PEI or glass with glue stick. NinjaTek gives room temperature to 50 °C, with glue suggested, and glue or blue painter's tape if you don't have a heated bed. Both makers say to use the cooling fan, NinjaTek from layer 2.

Feeding: direct drive, Bowden, and retraction

Soft TPU is hard to push through a long tube, and both makers steer you to direct drive, where the extruder sits on the print head. Siraya says Flex TPU 85A "is optimized for FDM printers equipped with direct drive extruders" and calls that setup "crucial for successful TPU printing." It also recommends mounting the spool directly above the extruder for the shortest path. NinjaTek's data sheet calls NinjaFlex "ideal for direct-drive extruders," and its product page says the "proprietary low-friction exterior allows for smooth feeding." Neither maker gives Bowden settings on the pages we checked.

Retraction pulls filament back to stop stringing, and soft filament can buckle if you pull too hard. Siraya gives a starting range, 1–3 mm at 1800–3600 mm/min, which is 30–60 mm/s, and says to "Start with short and slow retraction first." NinjaTek gives no retraction figure. Its troubleshooting guide says that if NinjaFlex prints with a matte or textured finish instead of its usual "smooth, glossy finish," you should "Try turning retraction off, then add small amounts of retraction back in." Our TPU compatibility guide covers direct drive, Bowden, and retraction in more detail.

AMS and multi-material systems

Neither maker mentions the Bambu Lab AMS on the pages we checked, so Bambu's own rules are the guide. Bambu's filament guide lists "TPU 95A/85A/83A/80A" as too soft for the AMS and AMS lite, and says such filament "cannot pass smoothly through the AMS / AMS lite channel." Bambu's notes for the AMS say to avoid "flexible materials, including TPU, TPE," because they "may get stuck inside the AMS feed tube." Those rules apply to 85A TPU whoever made it. Feed either spool from an external holder, ideally as close to the extruder as you can, as Siraya recommends. Our AMS filament compatibility guide collects Bambu's rules for TPU.

Drying and storage

Only Siraya publishes drying guidance. Its data sheet says "TPU filaments, including Flex TPU 85A, are prone to moisture absorption," and gives 50–65 °C for 4–6 hours in an oven if moisture absorption is suspected. It adds, "Filament dryer is not recommended because heating cannot maintain a uniform temperature throughout the dryer." For storage, it says to keep the filament in the supplied moisture-resistant aluminum bag, or in a dry box with desiccant below 15% humidity.

NinjaTek publishes no drying temperature or storage humidity on the pages we checked. Its data sheet does give a moisture absorption of 0.22% after 24 hours (ASTM D570), but that's a material property, not a drying instruction. Siraya publishes no moisture absorption figure, so there's nothing to compare it with.

Neither maker publishes a spool temperature rating, so check your spool before heating it. Our filament dryer vs dry box guide covers the options.

Same-standard test figures

These four figures are the only ones where both makers name the same test standard. They aren't a head-to-head result, because the samples were made differently, as explained below the table.

How the samples were made. NinjaTek describes its specimens in detail. They were printed on a TAZ 5 printer with a 0.75 mm nozzle. The tensile bars were Style IV dogbones at 100% fill with diagonal line fill and a 1.05 extrusion multiplier. The impact bars were printed un-notched, and the testing facility added the notch afterwards. The abrasion sample was a rectangular block, 5 × 0.5 × 0.5 inches, sized for a Taber abrader. NinjaTek also notes that different slicing, printing, and test conditions may give different results. Siraya gives no print settings or specimen details, only that its tensile stress and elongation at break were tested on the X/Y axis. It lists the impact and abrasion methods as "D256" and "D4060" without the ASTM prefix, and gives the abrasion figure with no unit.

So the abrasion figures match on paper, but we can't confirm Siraya's 0.08 is in grams, or that both samples were made and tested the same way. NinjaTek's product page also claims NinjaFlex's abrasion resistance is "20% better than ABS and 68% better than PLA." That's NinjaTek's claim, and Siraya makes no equivalent comparison.

We left these figures out of the table because the makers used different standards or gave no method:

• Hardness. Siraya tested to ISO 7619 and NinjaTek to ASTM D2240. Both are Shore A durometer methods and both report 85A, but they're different standards, so we list each in the spec table rather than treat them as one test.
• Tensile strength. Siraya gives 24 ± 3.0 MPa tensile stress at break to ISO 527. NinjaTek gives 26 MPa ultimate and 4 MPa yield to ASTM D638.
• Density. Siraya gives 1.16 g/cm³ to ISO 1183. NinjaTek gives a specific gravity of 1.19 to ASTM D792.
• Heat resistance. Siraya gives a Vicat softening temperature of 76 °C to ISO 306. NinjaTek gives heat deflection temperatures of 60 °C at 0.07 MPa and 44 °C at 0.45 MPa to ASTM D648.
• Melting point. Siraya gives 200 °C with no method. NinjaTek gives 216 °C by DSC.
• Toughness. Siraya gives 84 N·m·m⁻³ with no method. NinjaTek gives 82.7 × 10⁶ N·m/m³, calculated from its D638 stress-strain curve.
• Other single-maker figures. Siraya gives tensile stress at 100%, 200%, and 300% strain. NinjaTek gives elongation at yield, glass transition, and moisture absorption. Neither has a match from the other maker.

What each maker says it's for

• Siraya Tech Flex TPU 85A. Siraya describes a TPU softer than "common 95A TPU filaments," with a "soft feel closer to silicone," for wearables such as smartwatch straps and insoles, flexible connectors, vibration-damping pads, and phone cases. It says the filament passed ISO 10993-5, -10, and -23 testing for skin contact. That's a maker test claim for external-use wearables, not a medical or food-contact rating.
• NinjaTek NinjaFlex 85A. NinjaTek describes "the first flexible material on the market," with "excellent vibration reduction" and chemical resistance, and examples including sneaker insoles, helmet inserts, soft robotic grippers, and prototypes. Its product page lists REACH and RoHS 3 compliance.

Siraya Tech

Siraya Tech Flex TPU 85A (Black, 1.75 mm, 1 kg)

Best for

Soft wearables such as watch straps, pads, and flexible connectors on a direct-drive printer.

Skip this if

You need a firmer 95A part or plan to feed it through a multi-material system.

Specs, strengths, and limitations

Material

TPU (high-flow)

Diameter

1.75 mm

Net filament

1000 g (filament only, not packaged weight)

Hardness

85A

Format

other

Maker's nozzle range

200–225 °C

Strengths

• Manufacturer states it is more flexible than common 95A TPU, at 85A.
• Manufacturer states it is formulated for high flow and prints faster than typical 95A TPU.
• TDS lists 580% elongation at break.

Limitations

• Siraya Tech says it is optimized for direct-drive extruders and recommends mounting the spool directly above the extruder. It gives no guidance for Bowden setups or automatic material systems such as the AMS.
• Siraya Tech says to dry it in an oven at 50–65 °C for 4–6 h if moisture absorption is suspected (it says a filament dryer is not recommended) and to store it below 15% humidity.

View on Amazon ↗ (opens Amazon in a new tab)Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

NinjaTek

NinjaTek NinjaFlex 85A (Midnight Black, 1.75 mm, 1 kg)

Best for

Very soft, rubbery parts such as seals, gaskets, and grips on a direct-drive printer.

Skip this if

Your printer uses a Bowden extruder or you need fast print times.

Specs, strengths, and limitations

Material

TPU

Diameter

1.75 mm

Net filament

1000 g (filament only, not packaged weight)

Hardness

85A

Format

other

Maker's nozzle range

225–250 °C

Strengths

• Manufacturer states it has a low-tack, easy-to-feed texture.
• TDS lists 85 Shore A hardness and 660% elongation at break.
• TDS lists abrasion loss of 0.08 g over 10,000 cycles (ASTM D4060).

Limitations

• TDS describes it as ideal for direct-drive extruders. NinjaTek gives no guidance for Bowden setups or automatic material systems such as the AMS.
• Very slow printing: NinjaTek recommends 10–20 mm/s for top/bottom layers and 15–35 mm/s for infill.
• No drying instructions are published on the product page or TDS.

View on Amazon ↗ (opens Amazon in a new tab)Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Verdict: which should you buy?

Choose Siraya Tech Flex TPU 85A if…

• You print on a direct-drive printer and want 85A TPU with maker guidance up to 90 mm/s.
• You want the maker's own retraction, drying, and storage numbers to start from.
• Your printer runs best at a cooler nozzle, 200–225 °C.

Choose NinjaTek NinjaFlex 85A if…

• You print on a direct-drive printer and are happy to print slowly, at 10–35 mm/s.
• You want a data sheet that names its test standards and describes how the specimens were printed.
• You want a choice of 0.5, 1, or 2 kg spools, or 3 mm filament as well as 1.75 mm.

Safety and limits

How this page was checked

Every temperature, speed, feeding rule, drying setting, and test figure above comes from the manufacturer documents in the sources section, retrieved on 2026-10-09. We haven't printed with either filament for this page, so nothing here is a measured result of ours. NinjaTek's data sheet is a 2016 document, and when extracted, its property names sit one row below their values, so we matched each value to its test method and unit before using it. NinjaTek's product page and printing guidelines both give a 225–250 °C extruder temperature. Siraya's data sheet table and product page cite ISO 10993, the biocompatibility standard, but a note below the table says "ISO 10093," so we've used ISO 10993. Siraya's product page, data sheet and user guide don't state the filament diameter in their text, so we don't cite one for it. Values vary by color and revision, so check the current data sheet for your spool. Read more in our editorial standards and affiliate disclosure.

TPU: what to check before you buy a spool ↗