The UnKnown by MadHouse is a redesign of the popular 5150 made as a special limited run for the 2009 Worlds. The Worlds version has two different logos, whereas the main line has the same logo on both sides. The UnKnown features the same bead-blasting, anodizing, and shape as the 5150, but is two and a half grams heavier and has an A-sized bearing. This makes the yo-yo effective for 5A (Freehand). Moreover, it features laser-engraved artwork by IV on the side of the yo-yo.