DEFINATELY REAL HUMAN HAIR!!!! Dont go with the synthetic hair..........it's like doll hair! There are good and bad things about hair extensions! There are sooo many kinds and make sure you do ALOT of research on the type you want to get! Dont just go with anyone that does extensions! Make sure that they have done quite a few clients, and i would not recommend you get them if you have really really fine hair! My experience is a horrible one! I got the weft type extensions...........the hair is gorgeous! I planned on having them OHHHHH 6 months at the most, and it's now been 18 months! I am blonde with extremely fine hair! Each month i get them redone! Unfortunately the 2 people i went to didnt have alot of experinece. Anywayz......to make a long story short i have lost sooooo much of my own hair that i barely have any natural hair left! This has been very very tramatic....and i dont know when i will be able to take them out and deal! I have also heard horror stories about Great Lengths............cost about $1500 and your natural hair can either break off..........or dreadlock! It only lasts 3 months and then you pay another $1500! My hair lasts 4-6 months and each month i have them redone at $100. On the flip side (dont want to be totally negative) BUT.............IF you have thick hair then you may not have any problems! And some people dont have the problems that i have had! I will say it is alot of fun...............i not only did it for length............but i wanted a full head of hair! If you decide to get them make sure you get real human hair!