i just got a TX Shadow FX kit, and i'm not the biggest guy, as far as muscle...but i do have an athletic build and a little beer belly...lol!!!! 22 year old who likes to have fun!!!!!! straight out of the box, the bicep pieces just barely fit, if i bend my arm it'll bust open!!!!! same for the quads and maybe even the forearms!!!! i'm 6'0''200lbs. Shimming is def. a must for me!!!! hope that helps...FX is pretty slim but can be adjusted to for a better feel!!!! hope that helps!!!! this is my first kit, so i thought i'd start with a simple FX kit!!!! when i move on to the white armor, i'll go more movie accurate!!!!!