A simple, worth-while mod
For a visual mod, it is kinda cool. For functionality, apparently it helps w/ tuned FA20/24 NA or Turbo engines when you'd start tuning / pushing more power than stock. Supposedly, the dipsticks shoot out due to pressure. Typically a breather-styled oil cap would relieve this kind of issue but if you don't want and/or need something like that, this is the part for you. This part fits my 22 Subaru WRX, so it should fit on any other Subaru as well.
I wouldn't buy this unless it's on sale or heavily discounted though, 160$ retail is a bit steep for something simple like this.