Straightening or curling your extensions is possible with the ones sold on Canada Hair, as long as the hair quality is labeled "human hair" or "remy hair". Only these 2 hair qualities can safely be styled with hot tools such as a hair straightener or hair curler.
You can straighten your hair extensions for a sleek look or curl them to create voluminous bouncy curls.
You can style your hair extensions before or after you attach them, it all depends on which method is easiest for you! In order to preserve and extend the lifespan of your extensions, remember to always use a heat protectant spray prior to styling them & only use a low heat setting, since hair extensions are more fragile than our natural hair.
As for synthetic extensions, you can't use hot tools to style the hair since it's made of synthetic hair.