Its cold up there on the Moon. At least that is what those who ventured far tell us. That is, if they actually have been there... Here on earth it is less cold, so you don't need a full astronout suit but a jumper will do. Or a sweater if you prefer one of those. And on not too warm days, a pullover can also come in handy. Call him however you want: Michael is that piece of clothing that doesn't jump out there. That doesn't need to be the first, but is crucial into your surviving.
Note: in doubt about size? Take the larger of the two :)