Gym bags are bought on size, colour and price, and they are thrown away for one reason. These four decide whether that happens in a season or in five years.

Ask what the lining is

An unlined fabric body holds moisture in its weave, and that is where the smell lives. A coated, wipeable lining gives it nowhere to sit and gives you something you can clean.

It costs very little per unit, which is exactly why it is the first thing removed to reach a price, and it is invisible on a specification that lists denier, size and colour. Ask both suppliers what the lining is and you will often find the whole difference between two quotes.

Open the wet compartment and look at the seam

A real wet compartment is separately lined in a coated fabric and seamed the full height of the divider, with its own vent so it can dry out.

A panel pocket is cut from the same unlined fabric as the body and its seam stops short of the top. Anything that pools runs into the main compartment — the precise outcome the pocket was sold to prevent. Thirty seconds with an open bag tells you which one you are holding.

Count the mesh panels, and where they are

Ventilation is not holes. Air moving through a packed, zipped bag needs a way in and a way out, so a single mesh panel on one face does essentially nothing.

Mesh at opposite ends is what dries a bag between sessions. It adds very little to a unit cost and it is the difference between a bag that recovers overnight and one that needs a cleaning routine nobody follows.

Get both capacities, not the headline one

A shoe tunnel takes its volume out of the main compartment. A bag advertised at a headline capacity can lose a serious share of it to the tunnel.

Ask for the total and the usable main compartment separately, or you are comparing two bags on a number that means different things on each of them.

Treat antimicrobial as an addition, never as the plan

It is a treatment with a service life. It washes and wears out, and it acts on the fabric rather than on what is sitting inside the bag.

It is worth having on a bag that can dry out. It is not worth having instead of one.