Every AZIMUTH kit manifest lists a weight in grams beside every item, and every season somebody asks whether the grams are a joke. They are not. The luggage scale in the Chamonix office is the most honest colleague I have, and I include the other guides in that comparison. I have weighed every duffel that has passed through this office since 2024, and I remember the outliers the way other people remember weather.

Here is the arithmetic nobody escapes. Above five thousand metres your body is already losing an argument with the air. Every hundred grams on your back joins the other side. One hundred grams is nothing — until you carry forty of them, which is what an unweighed duffel always turns out to contain. Four kilograms of nothing is a summit margin, spent before you have laced your boots.

The method is dull and it works. Weigh everything. Write it down. Then defend, item by item, anything over a hundred grams. Not to me — to yourself, out loud if necessary. The most dangerous phrase in expedition packing is just in case, because it never travels alone.

What stays home, in my experience of reading other people’s duffels: the second fleece, which is the first fleece with worse memories. The full wash kit — soap does not work at minus fifteen anyway. The backup for the backup power bank. Two of the three books. Camp shoes heavier than 300 grams. Anything bought in the airport.

What never stays home, and is exempt from the ledger: spare headtorch cells, spare gloves, the repair kit, the personal first-aid pouch. Weight discipline is not minimalism as a style. It is spending grams where they buy margin and nowhere else. A 90-gram pair of spare liner gloves has saved more summit days than any item ten times its weight.

On supported expeditions the duffel limit is fifteen kilograms. Clients sometimes read this as a target. It is a ceiling, and the happiest climbers I have guided came in a kilogram under it. The manifest for each route is in the file, weighed line by line. Argue with it if you like — but bring the scale’s numbers, not your feelings.