Choosing lash extensions comes down to three numbers on the tray: curl, thickness (diameter) and length. Get these right for each client and your sets look natural, retain better and are easier to fill. Here is a practical guide to reading a tray and building a lash map.
Curl: how much lift you want
Curl letters describe how sharply the extension bends from the base. The two you will reach for most often are:
- C curl – a soft, natural lift. It suits most clients, works well on fairly straight natural lashes and is the safe starting point for a first classic set.
- D curl – a stronger, more open curl. It gives a wide-awake, dramatic look and helps on clients whose natural lashes point down or whose lids are hooded.
Keep in mind that the natural lash direction matters as much as the letter. A very curly natural lash paired with a dramatic curl can look stiff, while a downward-pointing lash may need extra lift to look balanced.
Thickness: match the natural lash
Thickness is measured in millimetres. As a general rule, an extension should never be heavier than the natural lash can comfortably carry.
- Classic sets (one extension per natural lash) commonly use 0.15 to 0.20 mm. Finer options like 0.15 feel lighter for clients with delicate lashes; 0.18 to 0.20 gives a bolder, more defined line on strong, healthy lashes.
- Volume and pre-made fans use much finer fibres, typically around 0.05 to 0.07 mm, because several extensions are applied to a single natural lash.
If you are unsure, go one step lighter. Over-heavy extensions are one of the most common reasons for poor retention and unhappy clients.
Length: build a map, not a single size
Most sets use several lengths placed across the eye. Common ranges sit between about 8 mm and 16 mm. A simple approach:
- Start shorter in the inner corner (often 8 to 9 mm).
- Build gradually through the centre of the eye.
- Choose where the longest point sits: towards the outer corner for a lifted, “cat-eye” finish, or in the centre for an open, “doll-eye” finish.
- Stay within roughly 2 to 3 mm longer than the natural lash so the set stays comfortable and secure.
Classic, volume or spike?
Classic lashes give a clean, mascara-like look. Volume fans (3D, 5D, 7D and up) add softness and fullness and can fill gaps in sparse lashes. Spike or wispy lashes are mixed into volume sets to add texture and separation. Many artists keep a range of each so they can tailor a set to every client.
Stock your tray
Browse our classic lash extensions and volume and premade fans in C and D curls, from 8 mm to 16 mm. Pair them with a reliable lash adhesive and primer and the right tweezers and tools, and finish with aftercare and removers for your clients.
Always follow the manufacturer’s instructions and your training for application, patch testing and aftercare.