I am 5'10", 190 lbs and bought a Large (I sometimes by an XL). The material is thin but OK (keep in mind it is polyester, not flannel). The jacket is a little snug, but acceptable. The pants.the pants is OK at the waist (36") but too baggy around the quads (and I do some weight lifting) and 3" too long (my inseam is 29 1/2"). Because the pants are baggy and too long to shorten, I'll be returning this tracksuit. If I was to get a size smaller, the pants might be OK but the jacket will be too tight.