Dupli-Arms grants Mezo a set of arm-like tentacles adjacent to his arms that can transform into duplicates of his other body parts. Mezo is able to reproduce any of his body parts, including ears, eyes, mouths, hands and so on, with said parts taking form through pods located at the tip of each of his tentacles.
The duplicated parts are actually enhanced versions of the original ones, which improves Mezo's strength and senses. Different parts can be manifested at once too, allowing Mezo to combine his augmented sensory abilities.
If for reason one or several of the replicated body parts are cut off, Mezo will can replicated it again once the injury is cured.
As part of his training, Mezo swiftly created multiple tentacles, with eyes and ears, to seek out the invisible Toru, all to increase his sensory capabilities.
The tentacles, just like any part of Mezo's body, are vulnerable to injuries coming from enemy attacks. The same goes for the replicated body parts. Although Mezo can regrow in any replicated body part that was cut off, it is still painful for him and takes time for the wound to heal.
Dupli-Arms makes Mezo excellent for spying and stake out missions, since his tentacle-created sensorial parts have heightened functions. For instance, with his eye replicas, Mezo has full peripheral vision that lets him see anything within a 360º field of view, and with his ear duplicates, he can detect sounds from sources behind walls or far away from his position. Mezo also prefers to communicate with others through reproductions of his mouth, due to the fact that he's always wearing a mask that covers his lower face.
For combat, Mezo multiplies his already great physical strength by replicating his arms, giving him force equivalent to around half a ton with just one set of his tentacle arms. Mezo is strong enough to carry more than one person on his back with little trouble, and he is further capable of shielding or hiding them from danger thanks to his Dupli-Arms having a webbed structure. This also means that the tentacles can function like improvised wings, letting Mezo glide for a limited amount of time.
The replicating pods, being a part of Mezo's body, can recreate even themselves as well, meaning that it's possible for Mezo to keep elongating his tentacles by just making those pods self-replicate over and over. Additionally, one pod can reproduce multiple separate organs, but doing so takes away some of Mezo's control over the duplicates, lessening their effectiveness.