Walter’s Filament Collection – Flexible


For all the people who have asked about filaments, here's my list, spread across 8 different posts.  This list includes over a hundred filaments, with pictures, measurements, and impressions.  All are 1.75mm. Please don't read too much into my opinions, there's a lot of variation in filament and printers, and my opinions apply only to the spools I have on hand.  I try to be objective with these opinions, but my preferences and biases affect my opinion, so keep that in mind when browsing this list. Also be aware of the date, some of these filaments may no longer be available, or may be different from what is currently available.  I sometimes describe how I use and print some filaments just to provide another data point, it's likely that your optimal setup will be different from mine. 


Diameter - Diameter readings are taken at several angles, across a meter or more of filament, at whatever part of the spool is currently accessible.  Sometimes the filament diameter variation is the result of variations in roundness, and may not have a significant impact on printing performance.  I've noticed that I've become less tolerant of filament diameter variation as printers get more precise, inconsistent layers or banding tends to overshadow filament diameter fluctuation.  One exception is with transparent filaments, where irregular layers aren't very visible.

Color - It's hard to know the exact color, transparency, and texture of the filament when you're buying online.  I'm hoping these pictures along with the descriptions will help you know what you're buying.  All the pictures were lit with the same basic setup (unless stated otherwise) so the colors should be somewhat consistent across different types and brands.  I have my monitors calibrated, and I try to adjust the pictures to match the actual filament as accurately as I can (which is not very accurately).  I don't put the same effort into the example photos or photos that contain multiple spools.

Transparency - Transparency makes a big difference in how these filaments print, but it's one aspect that I hard time getting reliable info on.  I'll use the following terms when describing the spooled filament.  This info is subjective, the surface finish of the filament will affect the perceived transparency, but it should give you a rough idea.

  • very high - Perfectly clear as far as I can tell, ignoring any color.
  • high - It's translucent, with a significant amount of fogginess or haziness.
  • moderate - It's opaque enough that it doesn't appear to be transparent, but light shines through it fairly easily.  If you press a bright flashlight against the spool of filament, about half of the spool will light up.  Infill is usually visible through one or two shell layers.
  • low - It's opaque enough that you probably won't see your infill showing through, but transparent enough to deemphaasize layer lines. If you press a bright flashlight against the spool of filament, you will see a large halo of light around the flashlight from the light filtering through the filament.
  • none - Completely opaque. If you press a bright flashlight against the spool of filament, you will see very little if any light bleeding through the filament.

Printers - I use a Eustathios Spyder v2 and a Rigidbot, both running E3D v6 Hotends.  The Rigidbot uses Printrbot gear head direct drive, the Eustathios uses a short bowden setup with a Bondtech extruder (160mm from gear to nozzle).  Both are fixed gap, symmetric grip, high torque extruders, so for the most part, all the filaments listed feed without jamming or clogging, (there are a few exceptions, like running metal powder filament through a 0.3mm nozzle or trying to print with cleaning filament).  I also used to own an Afinia H-Series Printer (US version of the Up! Plus), only a few of these filaments work well with that printer out of the box.  All the example prints have been printed on these three printers.  Keep in mind that filament isn't the only factors affecting print quality, choice of printer, experience, print settings, choice of slicer, etc. can have a bigger impact than the filament.

Environment - I'm not sure how much the ambient environment affects printing, but I live in San Francisco Bay Area, California, USA.  Temperature and humidity is moderate, indoor temperatures range from a low of 45°F / 7°C in the winter to a high of 80°F / 27°C in the summer with normal temperatures around 65°F / 18°C.  None of my printers are enclosed.

Links - There are affiliate links in this list, I may receive a small percentage of the total if you place orders soon after using the links (at no cost to you).  I've marked all affiliate links with an asterisk (*).  Many thanks to all who have been using these links!  Normally I only link to products I'd buy again, but for convenience and completeness, I'm linking all the filaments I can find a reputable source for (even the really bad ones, so read the description).  I usually link Amazon* when possible, unless I know of better sources for that particular item.


TPE (Thermoplastic Elastomer) – These filaments are usually the softest, most flexible filaments,  They’re elastic so they’ll stretch, but if you stretch it too far, it won’t return to its original shape.

TPU (Thermoplastic Urethane) – TPU feels like a hard rubber, it flexes easily, but doesn’t really stretch.  It’s quite strong and useful for functional parts.  Becomes almost rigid when it’s printed solid.

Bed Adhesion – Bed adhesion usually isn’t an issue with flexible filaments as any warping is usually compensated for by the flexing of the filament.  Printing on clean glass, as well as Aquanet hairspray will usually work.  If printing at 100% infill, the material becomes much less flexible, and is more likely to warp.  I’ll usually use Suave hairspray, or glue stick in these cases.




3D Supply Source Flexible | Red | 2015

Diameter: 1.75 – 1.78 | Transparency: None | Origin: China

I’m not sure what kind of material this is.  It isn’t elastic like TPE or resilient like TPU, it tends to hold its shape when deformed and it’s soft enough that you can press your fingernail into it.  It seems to print decently, but I haven’t really found a good use for it yet.

Sainsmart Transparent Red TPUIMGP1022IMGP3603imgp4589

SainSmart TPU* | Transparent Red | 2015

Diameter: 1.59 – 1.75 | Transparency: Very High | Origin: China

Vibrant transparent red color.  I ordered this spool directly from Sainsmart and it came on a small core white spool.  The TPU that I ordered through Amazon and came on a black spool was better.  Despite being undersized and wavy, it prints fine and looks good.

NinjaFlex FireIMGP9479IMGP9483IMGP9473IMGP9497

NinjaFlex TPE* | Red (Fire)* | 2015

Diameter: 1.67 – 1.75 | Transparency: Low | Origin: USA

NinjaFlex, in it’s various colors is one of my favorites as opens up new options for 3D printing and the quality of their filament is very consistent.  It does warp, but the flexibility of the filament will compensate for it unless you’re printing at 100% infill.  NinjaFlex fire is an attractive darker shade of red.


NinjaFlex TPE* | Orange (Lava)* | 2015

Diameter: 1.67 – 1.73 | Transparency: Low | Origin: USA

An attractive slightly red, orange color.  One of my favorite NinjaFlex colors.  It works well.


SainSmart TPU* | Transparent Orange | 2015

Diameter: 1.56 – 1.75 | Transparency: Very High | Origin: China

Vibrant transparent orange color.  See Sainsmart Transparent Red TPU above.  Diameter is inconsistent, I ran into several meters of filament where the diameter dropped below 1.4mm, which caused issues with my fixed width extruder setup.


SainSmart TPU* | Transparent Blue | 2015

Diameter: 1.66 – 1.70 | Transparency: Very High | Origin: China

I ordered this on Amazon, where it was advertised as a 1kg spool, but the spool only contained 800 grams of filament.  It took some effort to convince them that it wasn’t a 1kg spool and that the spool shouldn’t be included in the advertised weight.  They have since fixed both the description and the title.  I’ve also ordered spools from their site that were shipped directly from China (see red and orange SainSmart TPU above), but have significantly worse diameter consistency and arrived on different spools (small core white spools).  The pictures on Amazon seem to be switching to the smaller white spools so they may be shifting production.


NinjaFlex TPE* | Black* | 2015

Diameter: 1.70 – 1.74 | Transparency: None | Origin: USA

Arrives with a nice matte finish, but becomes much more glossy when printed.  Some overhangs can be challenging as the filament tends to curl up at the thiner edges.


Zen Toolworks TPU* | Black* | 2014

Diameter: 1.78 – 1.81 | Transparency:None | Origin: ?

I haven’t used this as much as it’s very similar to PolyFlex, but with a less glossy finish on the filament.


Polymaker PolyFlex TPU* | Black* | 2014

Diameter:1.68 – 1.75 | Transparency:None | Origin: ?

Works well, feels like hard rubber when printed.


3D Supply Source Flexible | White | 2015

Diameter: 1.73 – 1.76 | Transparency: Low | Origin: China

Opaque ivory color, turns very clear when printing, but returns to original color as it cools.  I’m not sure what kind of material this is, it’s soft enough that you can press your fingernail into it and the indentation will remain in the filament.  It prints fine, but I haven’t really found a good use for it yet.


NinjaFlex TPE* | Water* | 2015

Diameter: 1.68 – 1.72 | Transparency: High | Origin: USA

Comes with a matte finish, which gives it a frosted white appearance.  It’s significantly more clear after printing.


Zen Toolworks TPU* | Clear* | 2014

Diameter: 1.74 – 1.79 | Transparency : Very High | Origin: ?

Received this as part of the Zen Toolworks kickstarter, this is similar in flexibility / elasticity to TPU so I assume that’s what it is.  It is one of the clearest filaments I have.  Prints are very strong, and can be almost rigid when thicker parts are printed at 100% infill.  It warps quite a bit, but at lower infill rates, it’s not a problem as the flex of the material compensates for the warping.

IMGP3148 IMGP3149

NinjaFlex TPE* | Glow-in-the-dark (Neon)* | 2015

Diameter:  1.68 – 1.72 | Transparency: Moderate | Origin: USA

I haven’t tried printing with this yet.  It has a faint yellow-green tint, but it’s mostly white.  It doesn’t glow as strongly as the the brighter glow filaments, and glows more green-yellow, but it’s still bright enough to be useful.  There isn’t any detectable graininess to the filament as there is with most other glow filaments.

Notes on filament brands:

Atomic Filament - They target 1.72mm as the average diameter of their 1.75mm filament (according to their FAQ) so that's usually a good default diameter for their filament, their PLA is usually consistent enough that you don't have to measure each spool.  All their filaments are made in California (moved to Indiana in 2017) and they help support this site.

Colorfabb PLA/PHA* - The extra flexibility of PLA/PHA is great for thin, small, or flexible parts that would be too fragile to hold up with regular PLA.  It also prints with a satin finish that looks better than the glossy finish I usually get with PLA.  Despite the PHA content, I classified PLA/PHA with the other PLA filaments as these differences are fairly subtle and it prints with similar settings.

eSun* - eSun filament is sold and sometimes rebranded by a lot of different sources and I don't know if there are differences between them other than the different spool styles.  For this list, I assume they're the same.  Microcenter's Inland filament is currently eSun filament and the cheapest place I've found for it (if you don't account for shipping).  They also sell Inland* filament on Amazon with free prime shipping.  Most of the eSun filament in this list is from Intservo*, who sells on Amazon, but I have also ordered from Microcenter* and Prototype Supply*.

Inland Filament* - I assume all the Inland filament is from eSun (see eSun above) and I've mostly linked to Inland spools because it's cheaper and I prefer the solid black spools.

Honeycomb Drone* - Some spools are advertised as 3lb spools, but are standard 1kg spools.  Prices fluctuate on Amazon, I've seen prices under 10 and over 40 USD.  The spools I ordered were between 9 and 14 USD. 

3D Solutech* - Proudly claims that "All our materials are purely grow and made in the USA", but the spools and the labels under their stickers are identical to other filament I own that came from China.


Places to buy filament:

Amazon* - One of the best places to buy filament, I believe they even accept returns if you don't like the filament (I haven't tried that myself, that's partially why I have so much of it).

Printed Solid - They only sell the good stuff (Colofabb, Taulman, Fenner Drives, Polymaker, etc.), and are kind enough to send me some samples to try occasionally.  They sell filament samples which are great for trying out some of the more expensive filaments.  They also have a store on Amazon*.

Atomic Filament - Good filament, free shipping, made in California.  I check their site often as they're adding new colors / types regularly.

Microcenter - Good place to order eSun (branded as Inland) filament if you have a store nearby or are ordering large quantities (Shipping where I'm at starts at $6 and increases by $1 per spool).  They also sell on Amazon* with free prime shipping.