For several years now I've been using the cable and housing kits from Shimano and Campagnolo. The Shimano pre-cut short housing loop is 12 inches and the Campagnolo pre-cut housing loop is 13 inches. I've gotten into the habit of measuring them each time I open a new set and those lengths have been consistent over a period of about 8 years. I assume they both think they've got it right.