Alongside the iconic absence of eyebrows seen in Goku and Gotenks' transformations, it is heavily implied that long, flowing hair is also a defining feature of the Super Saiyan 3 state.

Super Saiyan 3 is Goku’s rarest used form because it’s not exactly efficient. Much as the long hair of the form implies, it’s a transformation that burns through energy very quickly and it ...

As viewers witnessed, Vegeta’s SSJ3 transformation looks a tad different from Goku’s and ironically harkens ... that would have still granted the Saiyans longer hair but would not curve ...