Review (4/5): good size. keeps my hair dry.
My friend loaned me a reusable shower cap one time and I loved it so much I decided I needed my own. I wanted to find something in a solid color because so many of them are patterned and very loud and that just isn't really for me. I mainly wanted the silver and gold ones, so I gave the pink and purple to the friend I borrowed the cap from so she has spares. I've used them a couple times and they seem to work well. They're big enough to fit all of my hair and my ears in them and they do a reasonable job of keeping the water out. The elastic band lets in a little bit of water around the edges, but that's to be expected. It's not enough to be a problem. The main part of the cap keeps the water out nicely, and the satin layer helps reduce that very loud noise that is caused by water hitting plastic.
As others have complained about, the band is a little bit prickly on the head. I don't have overly sensitive skin, so I don't notice it very much, but if that is something that would bother you, these may not be the right choice. I think a little head prickling is worth it to have the color and style I want, so it really isn't a big deal.
While the size is great for me (I have about chin length, very thick hair) I'm not sure if it would work if your hair was much longer (unless it was very fine). I use up just about all the space in the cap fitting my hair in it, but I also think I have a slightly larger than usual head.
Overall, it works for me and I'm happy with it.