The lederhosen hat was previously a reward from the Freaky Foresterrandom event. It can now be purchased for 500 coins from Iffie's Random Costume Shop, located in Thessalia's Fine Clothes store in Varrock. Like all other random event items, it gives no stat bonuses. The appearance of this hat looks similar to a Dark cavalier, and is sometimes used as a cheap substitute.
Currently, this hat suffers from the glitch in which the player appears to have short hair or is bald, even if they have long hair (e.g. a female character with long hair appears to have short hair when they wear the hat). Taking the hat off returns the hair to normal (many other hats suffer from this, including the Infinity hat).