Look at the sizes first before ordering!
It's best if you order at least +1 your actual size. If you are an M, make sure you order an L, otherwise it might not fit you.
There's also a sizes chart available as an image on this product page. Make sure you consult it.
But as I said, it's a safe bet if you do a +1 your actual size. If you wanna be more hip hop, you can even do +2, and that way you can't really go wrong.
Cheers! Have fun wearing this. You can choose symbols from Ruby, Weiss and Blake, so that you can represent the one you like the most.