Hello,

The Ceremony is approximately 16-17" thick. You will need the deep pocketed sheets to fit all the way around the mattress. If you are having something done custom, go with 17" so there is a tiny bit of leeway unless you prefer otherwise.

The Serta iSeries Ceremony is actually 15" thick. Although deep pocket sheets are not needed, they could be used. Another option is to get a set of DreamFit sheets. They have the reinforced elastic straps on the corners so they are sure to always stay on the mattress. Tucking in bottom sheet corners every morning is extremely annoying, and the DreamFits guarantee that won't happen. Hope this helps!!!