Knuckle Dusters are simple, blunt melee weapons worn over the knuckles of one hand that deal 1d4 bludgeoning damage on a hit and have the Attached, Light and Pugilist properties.

Properties

Attached
You can’t be disarmed of this weapon, but donning or doffing the weapon takes an action. You can use a hand equipped with this weapon to hold items, but can’t attack with the weapon while doing so. Additionally, you have disadvantage on attack rolls using other weapons held in a hand equipped with this weapon and on Sleight of Hand checks using the hand that is equipped with this weapon.

Light
When you take the Attack action and attack with a Light melee weapon that you’re holding in one hand, you can use a bonus action to attack with a different Light melee weapon that you’re holding in the other hand. You don’t add your ability modifier to the damage of the bonus attack, unless that modifier is negative. If either weapon also has the Thrown property, you can throw the weapon instead of making a melee attack with it.

Pugilist.
For creatures that roll a die when they make unarmed strikes (such as the monk), the size of their damage die is increased by one (maximum 1d12) when they make unarmed strikes with a hand equipped with a weapon that has this property.

Superior Strike

Flurry.
In a blistering display of speed, you make a number of unarmed strikes equal to 1 plus half your proficiency bonus (rounded down) against creatures within your reach. Each unarmed strike must be against a different target. You then gain a +2 bonus to AC until the start of your next turn.