Therm-a-Rest RidgeRest Classic

Backcountry.com says:
For lightweight durability, easy packing, and simple comfort, it's tough to beat the Therm-a-Rest Ridgerest Classic Sleeping Pad. Made with ultra-durable crosslink polyethylene foam with heat-trapping ridges, the Ridgerest has been around forever and hasn't changed much, because it hasn't needed to. If you're looking for simplicity and cost-effectiveness for the trail, you just can't beat it.