Size choose according to the your height,(From Head to toe!) For example: if you are 160cm tall, and standard body size(not too fat or too thin) should choose 160 size. hope you could understand.thanks! If taller than 175cm , then need to choose custom made.^_^ if there is anything you are not clear, could contact us any time. Package include: tail skin only(NO MONOFIN!!!!!!!) You can tell us your monofin size, we will try our best to make the tail to fit your own monofin! PS:we could also custom made for you. if you want, could send us the picture, then we will make for you.;) It is customize item.so it will not accept cancel when ordering, or return if the tail is no problem, hope to understand!!! tks! PS: please understand the size choose according to your Height, the tail is made of spandex, not silicone, hope could understand!