Compressibility
Synthetic insulation can’t yet match high-end down in terms of compressibility, but it can come close to that of 600-fill. But the bag still bulks out to 7- by 16-inches when full stuffed. 

Warmth
Mountain Hardwear’s Thermal-Q fill proved exceptionally warm, especially given its pack weight. Our range of testers all agreed that the HyperLamina Flame lives up to its 20º rating, keeping even cool sleepers warm in blustery conditions well below freezing. The slim, snug fit helps improve bag warmth by eliminating any and all air pockets that can trap cold air.

Features
The HyperLamina Flame makes use of Mountain Hardwear’s welded construction technology that eliminates stitching, which leaves holes that can bleed out heat (or let in cold as the case may be). The design also features a well-crafted hood that quickly and easily conformed to my head without constricting movement or vision. And I found I could make minute adjustments with minimal effort during the night.

The chest-mounted zipper proved to be a nice comfort-addition, especially since I typically sleep on my side, so the zipper wasn’t trapped under my shoulder. But the zipper also proved a bit problematic. It’s short length (about chin-to-bellybutton) made getting in and out of the bag a bit of a struggle, especially given the snug fit of the bag in general. It also eliminated the option of venting excess heat during the night through an open zipper. 

Overall Comfort
The snug fit was praised by the fast-and-light hikers on our test team, but for me (6’2” and 48” chest diameter) I felt a bit like a worm in a cocoon—I couldn’t wait to escape each morning. The narrow taper does reduce weight and bulk, but it really restricts nighttime movement. The hood was the one real comfort star. 

Durability
I frequently caught the bag’s outer shell in the zipper, especially when trying to get the zipper fully zipped during the night. Though the shell never actually tore, it did show signs of wear and abuse along the zipper edges, raising concerns about long-term durability.

Value
The Mountain Hardwear HyperLamina Flame performs well (especially for slender hikers and climbers who can tolerate the narrow fit), and is reasonably priced, making it a decent option within its price range.