I've redesigned my own business card more times than I've redesigned anything for a client, and I've still never printed it.
It's the smallest job there is, and the only one where you're your own client. Nothing pushes back. Every decision stays reversible, so none of them are really decisions. Do it for someone else and it gets easy again — their name is their name, their trade is their trade, and all you're doing is deciding what stays. A card is an editing exercise wearing a design brief.
Small doesn't mean simple. It means every mistake runs at full strength. Type has a floor, and you hit it here sooner than you expect — go under it and you haven't made something minimal, you've made a grey mark a stranger has to squint at while pretending to listen to you. A thumb lands on the corner every time the card changes hands, usually the same corner. Then it lives in a pocket and comes back soft.
90 x 55 mm is what Australia and New Zealand print, and Denmark, Norway and Sweden, and India and Vietnam — if the work is going to that half of the map, this is the rectangle. Cards live where people meet and can't count on being remembered: studios, architects, tattoo artists, barbers, the bowl by a café till, the trade show table where everyone's is white. The sets here run singles, stacks, fans, front-and-back pairs and cards held between fingers, on wood, concrete, kraft and dark stock.