The ProYo Cold Fusion Isotope-1 was the first in a series of slimline Butterfly-shaped metal yo-yos produced shortly before Duncan acquired Playmaxx. It featured a ball bearing axle which, combined with the aluminum body, makes for super-long spins. Don't forget the Brake Pad response system. The Isotope-1 also featured a satin finish, and comes included with four extra Brake Pads, two extra strings, and a holster clip. It is quite a limited yo-yo, as only 150 units were produced prior to the release of the Isotope-2.