sleeping bag specs

What lower comfort temps do you think a bag with these specs

450gr  of         850cu. in. (EU)         96/4 mix of down & feather  

Trapezoid construction 

Outer and Inner of Pertex Quantum 

Total bag weight of 830gr

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Let's say if the bag has a regular size i.e. fits people around the 1,80 1,90 max and normal girth you might expect to sleep surely comfy in such bag around freezing point. 850 cuin according EU-norm is top quality down (is >900 cuin U.S. norm)!

baffle height (loft height) with such filling weight should be around 7 to 8 cm on one side. EN temp rating comf woman around -5 C and Man around - 10

I sleep with 550 700 cuin (EU) comfy around freezingpoint. I expect from 450 gram 850+cuin EU more insulation value per gram due to higher loft.

Compare with PHD bags for instance the Minim 400 Down Sleeping Bag. Probably filled with 400 gram of 800 cuin down. rated -5 comfy, baffle height unknown but I guess around the 6-7 cm (lower cuin value)