Mountain packing fails in two directions: too much bulk, or the wrong layer at the wrong altitude. The fix is a system, not a longer list.
Three Layers, Nothing Spare
A moisture-wicking base, an insulating mid layer and a windproof shell will cover almost any mountain condition between them. Additional jackets mostly add weight and duplicate function.::Feet Decide Your Trip::Broken-in boots and merino socks matter more than any other single item. Never travel in footwear you have not already walked several kilometres in.::Altitude Changes the Rules::Above roughly 3,000 metres, sun is stronger, air is drier and cold arrives the moment the sun drops. High-SPF sunscreen, lip balm, sunglasses and a warm hat are not optional.::What Actually Gets Forgotten::A headtorch, a power bank that works in cold, any prescription medication in its original packaging, and a spare set of dry clothes sealed in a bag.