For those looking to increase their hair volume with hair extensions, the options are many. Clip-in hair extensions which amount to heavy weft of hair held on small metal clips are attached where they can remain unseen, typically in the very back of the head, underneath as much hair as possible so the clips don't show through the hair and the hair extensions become embarrassingly visible.
The beauty supply store and salons which offer hair extensions "on the side" offer a few options, links and rings and pre-bonded extension hair, a child of the parent "fusion" hair extension technique which involves manipulating a hot press gun to melt the glue into the hair or, in the case of the link hair extensions, a small metal plier to crimp the small metal tube around the hairs, creating a pressed, flat metal attachment…
But, you don't really want glues and metals in your hair, do you?