This year, we bought five thermal tights from some of the most talked-about Chinese underwear and functional apparel brands.
Instead of simply looking at the product pages, we wanted to do something a little different.
Look at the actual product. Turn it inside out. Look at the construction. And then put it on a real body.
What new ideas are these brands bringing to thermal tights?
What works?
What doesn’t?
And what can other brands learn from them?
Over the next five articles, we’ll take a closer look at all five.
Let’s start with SIINSIIN.
SIINSIIN: Thermal Meets “Light Shaping”
Founded in Hangzhou in 2021, SIINSIIN has built its identity around the idea of “light shaping” — combining shaping, comfort and everyday wear rather than relying on the stronger compression associated with traditional shapewear.
That makes its thermal tights particularly interesting.
Because thermal tights have always had a basic product-development challenge:
How do you add warmth without making the garment feel bulky?
And once shaping is added to the equation, there is another question:
Can you make the garment feel supportive without making it restrictive?
So let’s look at what SIINSIIN is actually doing.
1. Starting With the Packaging
The packaging is quite straightforward.
Both the inner and outer packaging use flexible plastic bags with customised branding.
For an online-first business, this is a practical choice.
Compared with rigid boxes, flexible packaging is less vulnerable to compression during parcel transportation, while also taking up less space.
Nothing revolutionary here.
But it is a good reminder that product design starts before the garment is even taken out of the package.
2. The Hand Feel Tells Us Something Immediately
The first thing that stands out when you touch the tights is the hand feel.
It feels much more cotton-like than many conventional thermal tights.
The fibre composition is also worth a closer look.
The label shows 22% cotton and 22% viscose, alongside the synthetic fibres.
Cotton and viscose are two different types of fibres — cotton is a natural fibre, while viscose is a regenerated cellulosic fibre — but both are interesting choices for a garment worn directly against the skin.
Viscose is known for its smooth, soft and breathable feel, while cotton brings softness, absorbency and a familiar next-to-skin comfort.
This is particularly relevant for thermal tights.
The consumer is not only looking for warmth. They also want the inside of the garment to feel comfortable against the skin, especially when the tights are worn for long periods.
So the use of cotton and viscose here seems to be doing more than simply supporting a “natural” or more sustainable product story.
It changes the wearing experience.
3. The Waistband Is Doing More Than Making a Statement
The waistband is probably one of the most interesting parts of the product.
There is a considerable amount of structural design built into the band, rather than using a visually simple waistband.
Part of this is clearly about brand identity.
The contrasting yarn colours make the structure visible, turning the waistband into something that contributes to the overall appearance of the product.
But the more interesting function is structural.
Look closely.
Most of the ribs run vertically.
Why does that matter?
A relatively high waistband can have a tendency to fold or roll downward during movement.
The vertical rib structure adds longitudinal stability and helps the waistband resist that tendency.
So one construction is doing two jobs:
It creates a recognisable visual identity, while also helping solve a real wearing problem.
But there is a potential trade-off.
More structure can mean less freedom to stretch and recover.
And this is where looking at the garment on a table is no longer enough.
We need to put it on.
4. The Back Panel: Solving One Problem, Creating Another
The tights are clearly based on a circular-knitting construction.
And that creates a familiar challenge.
The cylinder has a relatively fixed circumference, while the panty area needs substantially more horizontal room than the legs.
One common solution is a back insert panel.
For many Chinese consumers, this construction is completely acceptable.
For some Western consumers, however, the additional panel and seams can be less desirable.
But there is a reason manufacturers continue to use it.
It allows the panty area to gain additional width and can make a better-fitting garment possible within the limitations of the knitting process.
So again, there is a trade-off:
Better panty fit vs. additional seams.
The real question is whether those seams behave naturally with the surrounding fabric.
We’ll test that on the body.
5. The Fleece: Warmth Without Excessive Bulk
Inside the tights, the thermal effect comes from a relatively short, dense brushed surface.
This type of construction has become increasingly common in thermal tights.
The idea is straightforward: create a fine layer of fibres on the inside surface to improve warmth without simply making the entire garment much thicker.
And this is where the construction starts to make sense alongside SIINSIIN’s “light shaping” positioning.
The goal is not simply to make the tights warmer.
It is to keep them warm, close-fitting and relatively controlled on the body.
That distinction matters.
Because a thermal tight that is technically warm but bulky around the knees, ankles or feet is not necessarily a better product.
Now, Let’s Put Them On
Our model is 163 cm and 59 kg, which falls within the stated size range for M.
And this is where some of the construction choices become much easier to understand.
1. The Overall Fit Is Comfortable
The first impression is very positive.
There is no obvious area creating significant discomfort or excessive pressure.
For a product combining thermal insulation with shaping, this is important.
2. The Surface Looks Matte
The outer surface has a distinctly matte appearance.
There is very little of the shiny effect that many Chinese consumers tend to dislike in tights.
It gives the product a more understated and premium appearance.
3. The Shaping Is Noticeable — But Not Restrictive
There is a clear feeling of light compression around the legs.
But it doesn’t feel restrictive.
More interestingly, this light compression appears to help control the thermal fabric.
We didn’t see obvious bunching around the knees or ankles, and the fabric didn’t create the bulky appearance that can sometimes come with thermal tights.
This is perhaps the most interesting takeaway from the product.
The shaping function is not only about shaping the body.
It also appears to help control how a thermal fabric sits on the body.
That is a useful product-development idea.
4. The Waistband Actually Delivers on Its Promise
The waistband feels slightly firm when first putting it on.
But once worn, it remains comfortable.
We tested sitting, standing and walking, and did not see the waistband roll downward.
So the structural detail we observed earlier does seem to translate into a practical benefit.
This is exactly why physical testing matters.
A construction can look interesting on the table.
But the body is the real test.
5. A Smart Transition at the Foot
The foot area becomes noticeably thinner while retaining the brushed thermal surface.
This is a small detail, but a very practical one.
It keeps the foot from feeling unnecessarily bulky inside a shoe while maintaining the thermal feel.
Again, it is less about adding more material and more about putting the material where it actually matters.
What Could Be Improved?
The main issue we found was the back insert panel.
The two additional seam lines are quite noticeable.
More importantly, when worn, you can feel that the seam has a slightly different stretch behaviour from the surrounding knitted fabric.
The main body of the tights stretches relatively smoothly, while the seam area feels more limited.
It does not make the tights uncomfortable overall.
But from a product-development perspective, this is clearly an area worth improving.
Ideally, the seam construction should follow the stretch and recovery behaviour of the surrounding fabric more closely.
That would allow the additional panel to provide the necessary fit without becoming a noticeable point of restriction.
So, What Can We Learn From SIINSIIN?
For me, the interesting part of this product is not one particular technology.
It is the way several familiar solutions are combined around one clear product idea:
warmth + light shaping + everyday comfort.
The fibre blend changes the hand feel.
The brushed inner surface provides warmth without excessive bulk.
The structured waistband helps improve stability.
The light compression helps control the appearance of the thermal fabric on the body.
The thinner foot reduces bulk inside the shoe.
And the back panel solves a genuine fit challenge created by the
knitting construction — even though the additional seams introduce a new comfort consideration.
That is perhaps the most useful lesson here:
Every construction solution solves one problem while potentially creating another.
The best products are not necessarily the ones with the most technologies.
They are the ones where the different technologies, constructions and materials are balanced against each other.
And sometimes, you only discover whether that balance really works when you turn the garment inside out — and then put it on a real person.