Ordered 2 of these for my 3 year old sons  new Captians bed that has a guest bed stored underneath, also ordered from Wayfair. Came rolled so easy to storemove.    The description on the website said the mattress was 16cm deep, which is the max. depth that is required to fit underneath the captians bed. When it arrived the dimension was stated as 18cm. I was worried I would need to send back but after testing the already opened first mattress on the guest bed, it fitted perfectly. Good quality mattress, springy and comfortable with good support. Great price too. Very pleased with my purchase. Ordered on Wednesday evening and arrived on Friday morning.