Most hikers on an extended hike will carry either a self-inflating mattress, or some type of non-inflatable pad. The pictures show a purple mattress (not inflated) and a yellowish foldout pad. Either item goes under your sleeping bag.
If you are looking only for comfort, the self-inflating mattress (this one from Therm-a-rest) is the way to go—hands down. But there are advantages to the pad, and this Z-lite pad (also made by Therm-a-rest) is very popular.
I’ve settled on the non-inflatable pad, and here’s why.
Light weight–Pads weigh less than inflatable mattresses; this pad weighs less than a pound.
Indestructible–No worries about puncturing it, or wrecking the valve.
Convenience–Shake it loose and it’s ready to go. When I take a meal, especially in wet or rocky areas, it’s the first thing I grab to sit on.
Pack Support–As more hikers go ultralight with frameless rucksacks, this pad provides pack support.
I admit that I miss the cushy comfort of an inflatable mattress when I sleep. For convenience, however, especially on breaks, when you want to smother ants and insects with something other than your pants, when you want to rest and air out your socks and footwear, nothing beats the pad. So why not carry both? Well, one day I may.