Thats the lamb 5zip right? I own both the calf and the lamb in a 50 and the lamb runs big. I think its just supposed to have a slouchier fit. A year or two ago on oki-ni I saw the model wore a 50 in the calf and a 48 in the lamb. The lamb looked mega cropped but fit width-wise, which tends to be how its modeled online. I'd recommend staying TTS rather than down.