Shrinkies are a great method of hair extensions.
They are tough when installed but kind to the hair if correctly applied. Usually remove them after 3 months wear is recommended.
Shrinkies are a plastic type tube that fits around a stick tip then a heat applicator shrinks the Shrinkie down to a third of its size. Always squeeze the bond tightly with a rolling action to ensure there is no air in the bond. After 3 days the bond will be thoroughly dried.
You an get black Shrinkies or clear Shrinkies. On the tutorial the lady does not squeeze the bond when it has been applied but it is a good idea to do so to ensure that no air is trapped in the tube which would result in the bond slipping.
https://www.youtube.com/watch?v=2ETtb2H46cE&t=134s