When you choose your lash lengths and thicknesses to use you will have to take into account the strength and length of your client’s natural lashes.

• Strong natural lashes
For costumers that have strong natural lashes you can apply up to 0.15 - 0.20 mm thickness.

• For average natural lashes you would use up to a 0.12 mm thickness.

• For fine/ weak lashes you can apply up to a 0.10 mm thickness.

Although 0.10 mm thickness can be used on clients with thin natural lashes, remember that 0.10mm is a volume eyelash extensions so is designed to be use in multiples.
Therefore a single 0.10 will rarely give the client the look they desire and a 0.12mm should be favoured (unless you feel this is still too heavy)
If your costumers wish to wear the eyelash extensions daily then you must ensure you never overload the natural lash, and most therapists now rarely use over 0.15mm thickness to keep those natural lashes healthy.

Ussually you'll have:

• Costumers 20-30 years have thick natural lashes

• Costumers 30-40 years have medium natural lashes

• Costumers 40+ years have thin natural lashes

This is just a guide- you can have 20 years old costumers with super thin lashes or a client 50 year years old with very thick natural lashes, but usually your costumers will fall into this category because lashes tend to deteriorate with age.