What is this Runescape item?

Ok, so I've seen a few people walking around with this item and I'd really like to know what it is. Unfortunately the people disappeared before I could pester them. -sigh- But anyways, its like a whip. Only completely white. No not chain paint on Abyssal, like COMPLETELY white. And its like a whip in the way that you wield it, and its length and shape. Please help, because its bugging me! XD