How these collections are built
Photos are the actual images from the current catalog album for that brand and category, labelled with the style and colour. A photo appears in only one collection, so a page is a complete set for that brand and category rather than a mixed selection. Measurements and fit notes are collected from published references and cross-checked against several sources; where figures differ between sources, the range is shown instead of a single number, and the specific piece can be confirmed before you decide.
Why sizing is described per brand
Two bags from different houses, both called "medium", can differ by several centimetres in width. Two sneakers from the same house can be a full size apart depending on the line. Because the size word carries so little information on its own, each collection here leads with the figure that actually decides the choice — width in centimetres, strap length, heel height in centimetres, or the measurements Dior publishes for a relaxed fit.
How to read a collection page in two minutes
Start with the measurement table, not the photos. Find the width or length closest to something you already carry, then look at the images to see how that number behaves in real life. A Gucci GG Marmont small measures about 25.5 x 16.5 x 7.5 cm, which holds a phone, a compact wallet, and keys but not a tablet; a Speedy Bandoulière 30 at 30 x 21 x 17 cm swallows a 13-inch laptop sleeve and still closes. The number explains the photo, not the other way round.
Then check the naming trap. A Chanel "Medium" is a specific bag, not a midpoint between small and large, and a Louis Vuitton Nano Speedy at 16 x 10 x 7.5 cm is closer in capacity to a wallet on a strap than to its Speedy 25 relative. When a collection page shows two sizes of the same style, treat the centimetre difference as the real comparison: 5 cm of width is usually the difference between a phone-and-card bag and an everyday bag.
Finally, send the collection page link with the photo you have chosen. It confirms the brand, the style name, and the measurement you were reading in one reference, which is faster to answer than a screenshot alone.