Spare recurve strings are simple to attach please measure your existing string from tip to tip when stretched out to give you your required size. If you do not have an existing string please tell us what model crossbow you have we will then make you a string to fit Please let us know the make and model of your crossbow in the boxes provided, if you are unsure you can send us a picture to identify. If you have don't have your original string as long as you know the make and model we can make one for you.