"Its interior dimensions allow it to accommodate devices measuring up to 163 x 83 x 9 mm. Dimensions suitable for: Samsung Galaxy Note 2, Galaxy Note 3, Galaxy Mega 5.8, LG Optimus G Pro."
So I bought it for a Galaxy S7. It is 1 mm smaller, 6 mm less wide and 0.4 mm narrower (150.9, 72.6, 7.7 mm compared to Lumia 151.1, 78.4, 8.1 mm = Digitec specifications), but my additional protective flip cover (I always carry the phone including the cover in the Hektor bag) makes up for this, so it is about the same size as the Lumia. I still have a little more than 1 cm of space in the length and width. The manufacturer also confirms this on its website, specifically for the Lumia 950XL: http://www.krusell.se/en/products/mobile/microsoft/lumia-950-xl/#/filter#__s=pb=0;db=37;dn=824&__ob=n_a&__pn=1