One box consists of 4 masks. I usually use it with 3 days interval. I actually bought this product months ago at Etude House but I only used it last night. It's not like the usual masks which are one-piece. It is divided into two: one for the nose up and the other half is for the remaining part of your face. The mask was a bit big for my face but it didn't really bother me. I left it on for 20 minutes. After which, I massaged my face with the remaining essence, as directed, and went to bed. When I woke up, I felt that my face was hydrated and soft. I didn't notice the effects of the Vitamin C mainly because I don't have visible wrinkles and I'm still in the age when my body could still make enough collagen.
I may not buy it again after I use all masks because it's a bit pricey compared to other masks. For me, it had the same effects as the other masks from Etude House. They (the other masks) still leave my skin hydrated and soft at a lower price. I might try buying this again when I get older and the wrinkles become visible.