We're working out what we think - we'll add our view here!
Mountain Equipment says:
As efficient a bag as it is possible to make. Inspiring confidence even when water turns to ice, this ultralight bag will pack a punch in any high mountain environment during the late spring and summer.
*Mountain Equipment use their own 'Good Nights Sleep Guaranteed' rating which they believe is a more accurate number for some sleeping bags and is based not just on the EN test results but on lab testing, their own use, thermal imaging and cold chamber work, along with a lot of data analysis.