Is a 5-inch mattress thick enough for an adult?

For occasional use and lighter adults, yes. For nightly adult sleeping, especially on the side, a thicker mattress gives better pressure relief and lasts longer.

Will it fit a standard twin bunk bed?

Yes. It is a standard twin size, and the five-inch height keeps it below most bunk rails where a thicker mattress would sit too high.

Does the gel foam actually sleep cool?

It runs cooler than plain memory foam, but at this thickness there is little foam to trap heat. It is not an active cooling mattress.

How long does it take to expand after unrolling?

Most of the expansion happens within a few hours, with full shape in about 24 to 48 hours. Cooler rooms slow it down.

Does it need a box spring?

No. It works on a slatted frame, platform, bunkie board or RV bunk. Use a solid or closely spaced slat base so the thin foam is not felt through gaps.

Is it good for a toddler's first bed?

It is a common choice for toddler and kids' beds because of the low height and firm feel. Check that your bed frame and rail setup match a five-inch mattress.