Loaded with 800-fill down, the Sierra Designs Cal 30 boasts a remarkable amount of loft for such a light, summer-season backpacking bag. Though rated to 30º at its lower limit, the Cal 30 sleeps plenty warm as the temperatures approach freezing. The bag also proved to be one of the most comfortable in its class, though there were some fit issues for a few testers. (Note, the women’s version of this bag is the DriDown Clo 2).

Compressibility
The 800-fill and slick 10-denier nylon shell allow this bag to be stuffed into its cantaloupe-sized sack, and when space was a concern, we found we could further compress it to about the size of an extra-large grapefruit (like one of those Texas Ruby Reds on growth hormone).

Warmth-to-weight ratio
At just over 1.25 pounds, the Cal 30 has a very low carry-weight. At the same time, we found the bag to be one of the warmest in the class. It kept most testers truly comfortable in the lower-mid 30s. Indeed, by utilizing their full complement of extra apparel layers, a couple of our testers felt the Cal 30 would be a great bag for ultralight shoulder season trekking, even when the temps dipped well below freezing. Layering up proved more difficult for some, including myself.

Comfort
Everyone agreed that the bag has more than adequate shoulder and hip room when within the suggested temperature ranges, but I found it overly snug when I was wearing multiple layers and trying to use it in colder conditions.

One chronically restless sleeper also said it was a bit too snug for comfortable tossing and turning throughout the night. He praised the half-length zipper, however, he had no trouble with his legs rubbing on the zipper as he twisted throughout the night.

On the other hand, a couple of us found the half-length zipper limited the bags usefulness in warmer conditions since it lacked any way to ventilate the legs section. I also found the toe box plenty wide but just a little to short to comfortably contain my size 12.5 feet when I was lying on my back with my toes pointed skyward.

The hood fits nicely around the face and head, though, so if you do roll over in your sleep, the hood tends to move with you, keeping your face out and your head warm.

Durability
After repeated use by multiple testers, and two thorough wash cycles, we found a couple small snags/tears in the lightweight shell. Fortunately, the ripstop nature of the material works and the couple small tears remained very small. Unfortunately, the 10-denier weight should some susceptibility to snagging if carelessly handled. (One tester made a very small hole simply by slipping into the bag while a heavy DSLR camera sat on the footbox). The resultant tear was so small that no feathers were lost, but it did illustrate a potential problem.