Have had an Osprey Savu2 for a few months and quite impressed all told.
Big enough!
No hydration pack, but dedicated space for a standard bottle (with retainer).
In addition, fits a small pump, multitool, phone, keys, waterproof jacket, tubeless repair kit, tyre levers, patches etc etc. Could get even more in if I wanted.
But it’s a smaller and neater size than the Seral, and half the price.
Has taken a beating in the mud and wet of the last few weeks and still good.
Shop around and they are about £30 for the usual Osprey quality.
One minus point is that there are no external pockets on the side / waist straps – you can only use the pockets on the pack itself.
Osprey Seral 2 in Black – but shop around