This is a great fitting, high quality piece. One piece base layers are far more comfortable and warm that separate tops and bottoms especially if you spend lots of time in deep snow, skiing or climbing. This suit replaces an ancient Capilene one piece (not made for years). A size medium fits me ( 5'11" 150 lbs) perfectly. The material is stretchy, comfy, with variable thickness in appropriate places. It has a butt flap with small zippers on the upper leg for bathroom stops and a two way front zipper. I recently wore the suit under outer layers for a week of backcountry skiing in Canada with -35 c temps on one occasion- the suit worked perfectly, wicked well, never smelled and was totally comfortable. While it is pricey, Backcountry gave a killer discount and unlike a lot of Euro gear, Houdini actually makes their stuff in Sweden. Quality all the way.