At the same length and curl, two extensions will not give the same result if their thickness differs: the density of the look, the weight carried by the natural lash and how easy they are to apply all depend on it.
Here is how to choose the thickness of your eyelash extensions, from 0.05 to 0.20, according to your technique and the strength of the natural lashes.
What does eyelash extension thickness mean?
Thickness, or diameter, is expressed in millimeters: a 0.07 extension measures 0.07 mm in diameter. The smaller the number, the finer and lighter the extension.
It affects three things:
- the result, which is more or less dense and defined;
- the weight the natural lash has to carry;
- ease of application: the finer a fiber, the more precise the isolation and tweezers it requires.
Common thicknesses at a glance
| Thickness | Result | Typical use |
|---|---|---|
| 0.05 | Very light | Very fine fans, fragile lashes |
| 0.07 | Light and dense | Russian Volume, handmade fans. At GEMELLA: Athéna and Aura |
| 0.10 | Intermediate | Light volume, mixed sets |
| 0.12 | Soft and defined | Light Classic, mixed sets |
| 0.15 | Defined and bold | Classic. At GEMELLA: Hestia |
| 0.18 to 0.20 | Very bold | Classic on strong natural lashes |
These values are guidelines: every Lash Artist adapts them to their own habits, their adhesive and above all their client. The GEMELLA range focuses on two thicknesses: 0.07 for Russian Volume and 0.15 for classic lashes.
How to choose the thickness according to the natural lashes
A widely taught rule of caution: the extension, or the whole fan in Volume, must not weigh more than the natural lash that carries it. An overloaded lash weakens and does not hold as long.
- Fine, fragile or sparse lashes: favor fine, light fibers in moderate lengths.
- Strong, even lashes: they easily support a 0.15 classic set or fuller fans.
- Damaged or regrowing lashes: stick to fine fibers and short lengths while the lash regains its strength.
Thickness and number of extensions per fan
In Volume, thickness is chosen together with the number of extensions in the fan. The more extensions a fan contains, the finer each fiber must be to keep the total weight reasonable: fans of 3 to 6 extensions are commonly made in 0.07 or finer.
For classic lashes, a single, thicker extension is applied to each natural lash.
Round or flat extension: the case of Flat Velvet
A flat extension, such as Hestia, Flat Velvet 0.15, gives a visually more intense result than a standard round extension, while keeping the set light and refined. It is a way to get more definition with classic lashes without weighing down the look.
Which thickness to start with?
A 0.15 extension is easier to pick up and isolate: it is the one you learn to apply first, with classic lashes. Fine 0.07 fibers require flawless isolation and precise tweezers, because even the slightest neighboring lash stuck to them shows straight away. That is why Russian Volume is learned after the basics of classic lashes.
To practice on a small budget, the Athéna MIX 4–6 mm and Aura 5 mm mini boxes are available in 0.07. Your choice of tweezers matters too: our guide to choosing your eyelash extension tweezers will help you equip your workstation.
Common mistakes
- Choosing a thicker fiber to get more volume: the result is heavier, not more beautiful.
- Forgetting about length: a thick, long extension weighs more than a thick, short one.
- Using the same thickness for every client, without looking at the strength of their natural lashes.
- Thinking about thickness on its own: it is chosen together with length and curl.
In summary
A fine, light fiber for Russian Volume fans, a thicker fiber for a defined classic set, and always an eye on the strength of the natural lash.
Find 0.07 in Athéna, black Russian Volume and Aura, brown Russian Volume, and 0.15 in Flat Velvet with Hestia. The whole range is in the Eyelash extensions collection.
To learn how to choose the right thickness for each client, Débo Beauty in Geneva offers a classic lashes and Hybrid Volume training and a Russian Volume Perfect Volume training (taught in French).