At 0.07 thickness and under is considered thin enough for safe volume lashes. Of course, that depends on your client’s
natural lash health.From thickness of 0.10 and up can be used for classic lashes extension
The difference between these is the weight of the extensions.Depending on the look your client is going for, you can determine whether they want Classic or Volume style, and choose the to create that look.
Beside thats, there is also the Hybrid Lash Style, which is when you use lashes from both classic and volume trays to mix together.