Make a ranged attack roll with an attack bonus equal to your Dexterity modifier plus your proficiency bonus. On a hit, the target is restrained until you take a bonus action to speak the command word again to release it. Doing so, or missing with the attack, causes the bands to contract and become a sphere once more.
A creature, including the one restrained, can use an action to make a DC 20 Strength check to break the iron bands. On a success, the item is destroyed, and the restrained creature is freed. If the check fails, any further attempts made by that creature automatically fail until 24 hours have elapsed.