Weight Disk: Weight Ring
A metal ring with 12 notches, only compatible with Hayate Base and Hayate Base (Hasbro) - also note that it counts as a Weight Disk thus cannot be squeezed onto other Beyblades legally.
Lightweight, and can spin a little freely which results in terrible inertia-related issues when launching and in battle, where hits to the weight disk can cause very heavy interruption to spin.
Nonetheless, it is technically not the lightest Weight Disk (that being the soft-edge mold of Eight Wide), and does have an extremely edge-focussed Weight Distribution, which does tend to aid the Hayate Bases to be somewhat less dismal than they might otherwise have been - after all, Mexico's champion for the World Championships did use Tiger Defenser on Hasbro's Hayate Base to win.
No real use, however.