Konstrux' Tail Twister is undeniably the nicer-looking one, but it does have some overhangs due to it being round. Especially the very tip might produce gaps by sinking filament, and as you want to push this through your hair, it may get tangled easily. That's why I redesigned it in an octagonal shape - you won't notice it's not round, but it's easier to print.

As I have pretty fair hair, the original design was too bulky for me and I'd have to pull out the hair tie too far, so there's a second one with a smaller loop.