The Kanohi Garai was the Mask of Gravity. It allowed its user to increase or decrease the effect of gravity on a target.1
Notes
The Kanohi Garai was the Mask of Gravity. It made Hewkii one of the fiercest Toa Mahri in a fight.2
The Kanohi Garai was the Mask of Gravity.3
If a Toa of Gravity put on a Garai, it would really make no difference for him. It wouldn't allow him to do anything he couldn't do.4
The Mask of Gravity was an offensive mask, so it could control the gravity of others.5
A Mask of Gravity was likely made from a disk of gravity. That didn't necessarily mean the disk would have to be from a specific Toa; it could've simply been an elemental powered disk.6
The Garai was very powerful and comparable to Nuhvok-Kal's abilities, but Hewkii didn't have the experience working with gravity that Nuhvok-Kal had.7