Having a hairpiece made from your own hair sounds good in theory, but it is rarely a good idea.
1. How long is the hair? If it is less than 10", it can't be used. The only exception is if you have a ThinSkin piece made with injected (not knotted) hair.
2. When you cut the hair, did you tie all of the hairs into a ponytail, making sure that the root ends are all together? If not, you'll end up with a rat's nest of endless tangles.
3. About 40% of the hair in a ponytail cannot be used (and has to be removed) because it is less than 50% of the total length of the ponytail itself. If this does not leave enough hair remaining, the factory will need to add their own hair to your piece.
4. The hair used in high quality hairpieces has never had anything but shampoo and conditioner used on it. If you regularly put product in your hair or blow dry it, that compromises the quality of the hair.
The bottom line is that it is almost always best not to use your own hair.