This is a shameless plug for the bag I carried - or wheeled, rather - around Spain for three weeks.
Because, unlike some past trips, not once did I ever find myself complaining about distance to walk finding hostels, how many times I'd have to lug it between hostel, bus -plane home, even.
It was small enough to carry on the plane and easy to sling into luggage compartments, didn't impede anyone's progress on city buses, held up through rain, didn't skew sideways on cambered roads or pavements, etc. etc. etc.
No matter how tightly packed it was easy to pull along.
The zips and seams are strong, as is the fabric. And it has a five-year guarantee, which means the manufacturers expect it to last much longer. I think they're probably right.
I don't treat my bags like flowers; I expect them to be like me - a bit rugged and up for the odd spot of mountain walking if the urge takes me.
Now I'm somewhat older, so prefer not to take a backpack except where conditions mean this makes for easier going. In Spain I didn't need to check out the backpack facility so can't comment on this, except to say it zips away very neatly and safely when not in use and the straps cover rolls back and fastens without coming off, so you can't accidentally lose it.
It measures 55x40x20cm (22x16x8 inches). There's also a separately zipped pouch on the front, big enough to hold a laptop and/or maps etc. Capacity is 44 litres (2685 cubic inches). And it weighs only 1.7 kg (that's 3.75 pounds for those using imperial measures) which is wonderfully light for all that it offers.
Fabric is Cordura and it comes in a variety of colours, including black. Mine was a rather fetching royal blue.
Possible minus points to note:
The backpack facility lacks a waist belt. As I haven't tested this facility I don't know how much difference this makes when travelling from city to city, for example.
If you have to carry it upstairs there's only a small (but comfortable) handle on the top; an attachment for shoulder strap would have been handy - though I managed it easily up three flights of stairs, so not really a problem.
OK - the nitty-gritty. It's called Cabin Max. The company is in Lyon I think. Amazon UK sell it for around £30. I think it retails for a much higher price in the USA, though. However, I've seen similar bags selling fr at least three times the price. I can't praise this one highly enough.

