Therm-a-Rest Z Lite

The Therm-a-Rest Z Lite is the iconic accordion-fold closed-cell foam pad, made from moulded crosslinked polyethylene. An R-value of 1.7 puts it on the lighter end of 3-season insulation — not enough alone for winter, but useful as a supplemental layer under an inflatable pad, boosting total warmth while protecting the air chamber from punctures caused by sharp rocks or sticks underneath. Unfolded it measures 183 × 51 cm at 2 cm thick; folded, it packs down to roughly 51 × 14 cm and straps to the outside of a pack with no stuff sack needed. The closed-cell structure doesn't absorb water, so it keeps working reliably in rain or on wet ground where open-cell foam or down would struggle. At 397 g, with no valves or air chambers to fail, the Z Lite carries essentially zero risk of a mid-trip failure — unlike an inflatable pad, it can't puncture its way out of usefulness. The trade-off is reduced sleeping comfort compared to air pads, which is why many hikers pair it with a thinner inflatable rather than relying on it alone.