I was skeptical at first but i wanted to try something different than my bulky scuba diving wet suit style sauna top and bottom i purchased a year ago...this material looks almost like a regulat tee shirt and i saw reviews from different brand names so i tried this brand. Im one of those guys who has a hard time breaking a sweat especially in my gym where there are fans on every corner...i even wear a winter scully year around in the gym to try to break a sweat ...within the first 3 minutes of putting this on i felt my core heating up and by the time i was 5 minutes into my workout i could feel perspiration dripping inside the shirt and the bottom shorts made from the same materials under my sweat pants were also dripping sweat down my legs ...this inspired me to want to sweat more thus amped up my intensity and enthusiasm..i knew i sweated but i had no idea how much until i lifted the top and to my surprise sweat rained down on the floor like in the video about this product..i have never sweat that much lifting weights before ..im going to wear it in the evening when i get in my muay thai bag workout...that should bring the heat! I ordered 3x as my chest is 50in...it fit perfect with a slight snug fit around the shoulders but my shoulders are wide so i have that problem when it comes to shirt size....im going to order a second top to wear at work....if you are doubtful then rest assured this wont disappoint! And this is coming from a hard to perspire guy in the gym. . it was a wise purchase!