MEC Kelvin 3.8 Sleeping Pad

When inflated, it's three times thicker and up to twice as warm as a 1/2" closed-cell foam pad. And when rolled up, this pad takes half to a third the space (volume) of that same closed-cell foam pad.

Size - rolled: 30 x 16 cm (12" x 6")
Size - inflated: 183 x 51 x 3.8 cm (72" x 20" x 1.5")
Weight: 775 g (1 lb 11 oz)

Thickness - 3.8cm (1.5"):
This is pretty average for these "self-inflating" type sleeping pads. They called it a "Medium-Thickness" pad in the literature. For a side-sleeper like me, this was the bare minimum to keep my contact points elevated off the ground (anything thinner, and I would have displaced the air under my shoulders and hips and been uncomfortable all night).

Warmth (2.8-3.2 "R"value):
This is a biggie for sleeping pads. In the summer it's not so important, but in the shoulder seasons it makes a big difference. this pad wasn't the greatest at keeping you warm in cooler environments, but it was better than using a foam pad. These days, there are much warmer varieties, but you pay a premium for warmth.

Firmness:
As you can mouth-inflate these pads to your own liking, this is a matter of personal preference. I like my sleeping pads to be firm, and this pad delivered (up until the point of failure a few years later, when it would no longer hold air pressure).

Packability: 
These types of sleeping pad must be compressed when rolled to "deflate", and then the valve closed to keep the internal foam from re-expanding the pad again. It can become a little tedious if you're moving campsites every day on a multi-day route, but the tradeoff is for much better packed volume compared to standard foam mats. 

Construction & Durability:
After a few years of light and occasional use, my sleeping pad failed due to a membrane degradation/decay in the "top" fabric. it was pretty spectacular to do the soap-test expecting to find an isolated pin-prick, and instead see the whole surface foam up! Luckily for me, MEC stands behind their products, and for only a small fee I was able to upgrade to the newer MEC Reactor 3.8 sleeping pad. So while I can't say the build-quality was the absolute greatest, the customer support from MEC is phenomenal!!

This is the inflated sleeping pad... Nothing you wouldn't expect.

This is the business-end of the pad... your mouth will get very well-acquainted with this.

Unfortunately I cannot take credit for the photos. I no longer have my sleeping pad, as it had to be returned. I scavenged these photos from the internet. Plz forgive me! LOL

Background

This was my first "self-inflating" style sleeping pad. I bought it new in 2008, and it gave up the ghost in 2015. During that time, I likely used it for a dozen or so weekend trips, and maybe up to five full-week trips, all in the summer months. I felt I didn't use it a LOT, and as a rule I take good care of my gear, so I was disappointed when it failed. In the end, it suffered a full membrane failure on the "top" surface, which allowed me to take advantage of MEC's Lifetime Product Guarantee and upgrade for a small fee to their newer MEC Reactor 3.8 sleeping pad (review pending...).