Steel knuckles take the form of four linked metal rings in a shallow convex formation with a bumper attached to the concave face. The rings are slipped over a combatant's fingers with the bumper pressed into the palm of the hand. When a punch is thrown, the knuckles take the majority of the impact impulse, transferring much of the punch's kinetic energy to the target by way of the harder, smaller impacting surface of the metal knuckles. This drastically increases the likelihood of serious tissue disruption and bone damage.
The steel knuckles do slightly more damage per hit than its brass or spiked counterparts, but it really shines when used in V.A.T.S. The steel knuckles use only 14 AP to be swung, giving it one of the lowest AP costs for any weapon. As such, it's great to use with the Paralyzing Palmperk.