What it physically is
A stainless steel bottle with a white coating, 500ml, printed with your picture. One size and one colour, which keeps the decision to a single question: which photograph.
Which photographs suit it
The print area is a tall, narrow rectangle wrapped round a curve, and that shape is unusual enough to be worth thinking about. Uprights work: a signal gantry, a station nameboard, a locomotive head-on, a lamp post and a bit of platform. A wide landscape shot has to be cropped hard to fit, and usually loses the thing that made it good.
Like the mug, it asks much less of a file than wall art does, so this is a use for the picture that was never going to print large.
Getting the crop right
Keep the subject in the middle third of the frame and leave some space above and below it. The picture runs round the body, so anything near the side edges ends up round the back, out of sight when the bottle stands on a bench. A phone photograph taken upright is often a better starting point than a camera's landscape frame for exactly that reason.
A restyle helps a busy picture here as well. The ink and wash style thins out a cluttered background, which leaves the locomotive or the signal standing clear against a pale wash.
Who it is for
Anybody who spends real time at the end of a platform, on a lineside footpath or at an open day in February. It's a practical object first, which is exactly why it gets used more than a novelty gift ever would, and it's the one thing in the range that other enthusiasts will actually see.
The alternatives
For the desk rather than the bag, the mug. The stage page lists everything we print on.