This thing is amazing. One piece is the way to go!! Definitely the best protection from cold air and snow. The hood is amazing! I generate a lot of heat quickly when I start exerting, and I cool down just as fast when I stop exerting - the hood design is key -- easy up and down at any time to help me regulate temperature and stay comfy. The Merino wicks great, doesn't smell ever, and has a wide comfort range. The rear poo poo zip is super easy to use. I wear this thing camping, riding, split-boarding, snowshoeing, as pajamas, sleeping bag liner, under a drysuit while whitewater rafting in cold weather, and I'm sure I forgot some other uses. The Ninja Suit has definitely worked its way into my top 5 pieces of gear ever. It took forever for me to convince my Dad to try one (he runs hot too), but once he did (on our Grand Canyon trip) he was hooked 100%. Didn't take it off for 5 days straight. I could go on... but anyway, Ninjas rule!