These are great - BUT, that depends on how full/thick your hair is. My hair is full, wavy, with loose curls, but I found these to be too big for a ponytail - a size down was too small. I can manage to force the smaller ones to close around my wet hair (in a high ponytail after I wash it) while it air dries, but it is a battle. The minis (these ones) are too big, but I do use them on days where the micros just won't close. Wish there was an in-between - I love using them to keep my hair up and out of my face while it dries.
Note on the plastic - I was worried it would be flimsy, but its not! All of mine have lasted, and I haven't been very gentle with them.