That looks to me like scrunched strips of fondant, rather that butter cream.
Icubed83, I would agree with you and thought that at first till I saw various pictures that give the recipe for the cupcake and the frosting but no tips on how to do the ruffle.
the icing looks flat so it may be the carnation tip.
I'm not so sure it's the 150. It could be from one of those 'new' sets (maybe 15 yrs ago now haha) But there was a set of tips that did similar designs. I think today they can purchased separately but can't recall the #s anymore.
I'm not so sure either, it could just be a rose tip. Sometimes you just have to go to the source for the answer.