Was looking for a decent power bank for my Nexus 5X, e.g. with a USB C output, and came across this.
Compact, with a 10000mAh capacity, comes with a USB C output, as well as being QuickCharge compatible.
As an added bonus, you can also get a 6 port 60W desktop USB charger with it, free of charge, which also takes you temporarily over the £20 mark for free delivery. The cost is deducted on checkout.