Can't beat the price per pack ounce lost. I have used this bag in Shenandoah in the fall and will also vouch for its rating all the way down to 40 (easily) in a tent. After a summer & fall of heavy use my bag still looks new. Compresses down to about nalgene size easily. As with all ultralight gear, you have to be a bit more careful when zipping, storing, etc., but the benefits are worth the extra care requirements.

Great bag, super light, super compact, and comfortable all the way down to 40. I've used this bag several times in early spring at virginia beach, where the temps at night were sometimes down below 40, and with a thermal top and bottoms, I was totally comfortable. Great bag for summer camping/backpacking.

I chose this bag to include in my UL summer base pack. It's super light, packs really small (actually comes with a pretty useable compression sack), and while it's light, seems durable enough to stand up to some abuse and not complain too much. I paired mine with a silk mummy liner and tested it out in my backyard on a 33 degree night and was comfortable enough that I never woke up due to the cold, and there didn't seem any cold spots.

For summer/autumn camping, this bag can't be beat. Footbox is spacious. Zippers don't seem like they'll have snagging issues. The only problem I had with this bag is that there's a small pocket on the inside that uses a Velcro closure that might chafe your mummy liner the wrong way. I took that Velcro piece out with a stitch remover tool, problem solved.

Lafuma did really well designing this bag.

As far as a lightweight warm weather sleeping bag, this Lafuma x650 Pro is great! Hardly adds any weight or takes up any space in your pack. Construction seems solid although I have not had mine a full season. I have slept in it when the temps dropped into the mid 40's and was comfortable with just thermal underwear and a sleeping pad out in the open. I would not want to be caught in a chilly early spring or late autumn night with just this bag but for the price, the quality construction, compressing stuff sack, weight, and stuff size, this is a quality purchase that I would recommend to friends.

This bag is very compact and light weight. It stuffs down to a size of a nalgene bottle. It saves a lot of room and weight to your backpack. The bag can even fit into one's day pack. Im 6 foot and the bag was perfect for me. My only problem was that I woke up very cold in my tent. The temp was around in the mid 40's when I was awaken. I used this bag over the summer and it turned out to be great. What was pretty cool when it rained the bag still kept me warm in the summer and dried quickly. If one is looking for something light for the spring, summer, and fall mounths get this bag. But wear a thermal underneath in cooler temps.

this bag is great for warmer weather- would not trust it for anything below 45 degrees though. VERY LIGHTWEIGHT AND COMPACT- must buy for this reason alone!

Wow this packs small and light!! I'm cold blooded and my husband well - .. he's a furnace. With sleep pads I used a 0 degree bag and he used this one on our most recent backpacking trip. The temp got down to 35 degrees and I was still cold but my husband said he slept just fine and that he will only use this bag from now on. It did take me few tries to get the bag back in the stuff sack. If you're warm blooded and like to travel light this is the way to go.