I purchased the Hilltop Packs Sit Pad Ultralight because it's description indicated it was substantially lighter than my Thermarest Z-Pad and I was curious how it would compare to the Z-Pad. To begin with, my Z-Pad weighs 59 grams (2.1 oz) while the Sit Pad Ultralight I received weighs 32 grams (1.1 oz). The weight difference is primarily due to the smaller size of the Sit Pad Ultralight. My Z-Pad is 1-1/4 inch wider and 1/2 inch longer than the Sit Pad Ultralight. Additionally, the Z-Pad is slightly thicker than the Sit Pad Ultralight and is made of a more rubber-like material, which makes it a bit more comfortable to sit on when on rocky terrain. I'm not too concerned with the smaller size of the Sit Pad Ultralight. It provides reasonable coverage for my bottom and has proven effective in keeping it free of dirt and debris, which is what I want most from a sit pad. Another difference worth noting is the folded size of the pads. The Z-Pad, when fully folded, is narrower than the Sit Pad Ultralight but it is also thicker than the Ultralight. This may or may not be an issue for you. It hasn't been an issue for me. As a matter of fact, I prefer the wider folds of the Sit Pad Ultralight as it makes it easier for me to set it on edge (accordion-style) and use it as a wind screen for my stove. The only real concern I have with the Sit Pad Ultralight is with the long term durability of the pad's hinge points (fold lines). The fold line material thickness on the Sit Pad Ultralight is less than that on the Z-Pad. Only time will tell if this concern is warranted. Overall, though, I believe the Sit Pad Ultralight is worth considering, especially if you're looking for ways to shave ounces from your pack.