Black Receiver

These black rods, which serve as chakra receivers, are created from Madara Uchiha's will materialised into a physical form. Those who possess the Rinnegan are able to transmit their chakra across vast distances to these receivers through an application of the Outer Path. The black rods serve a variety of purposes and come in various shapes and sizes.

Background
When Obito Uchiha first awakened his Mangekyō Sharingan, a number of these black rods, along with several branches created through Wood Release, emerged from the right half of his body, which was made up of genetic material from the living clone of Hashirama Senju created by Madara. In a fit of rage, Obito then slaughtered all of his enemies who were present, coming to his senses by the time night had fallen. Prior to his death, Madara materialised his will into a black rod that extended from the navel of Hashirama's living clone, which both he and the Demonic Statue of the Outer Path were connected to at the time. Madara told Obito to make use of the black rod for the Six Paths Technique.

During the Third Shinobi World War, when Hanzō forced Nagato to kill Yahiko in exchange for Konan's life, Nagato used Madara's Rinnegan to summon the Demonic Statue of the Outer Path. Several black rods then extended from the statue's navel and pierced Nagato's body, at which point he used the statue's power to kill Hanzō's followers, leaving him in an emaciated state. Nagato would go on to develop the Six Paths of Pain, a technique which allowed him to manipulate as well as channel the Rinnegan's abilities through six corpses by piercing them with chakra receivers and transmitting his chakra to them through the receivers embedded in his own back.

Because these black rods originated from Madara's will, he has the ability to control whoever has them within their bodies through the use of his chakra. The resulting takeover covers the target's body in black matter.

Overview
Each variation of the charka receiver allows the user to transmit their chakra across vast distances. According to Shizune, these receivers act as high-frequency chakra demodulators, which become appreciably warm to the touch whilst currently receiving chakra. They possess incredible durability, damaging every scalpel Shizune used to extract just a small sample during her autopsy of the first Animal Path, and even displaying some resistance when struck by Naruto's Rasengan. When employed offensively, they have shown to be capable of easily piercing through their target, even if the later is a tailed beast.

Chakra Receiver Rods
Nagato upon summoning the Demonic Statue of the Outer Path during his confrontation with Hanzō of the Salamander was pierced by several of these all of which originated from the navel of the statue. From there, he incorporated their use in his Six Paths of Pain technique, where he implanted the receivers into a number of corpses at various points along their body, much like piercings. Doing so allowed him to transmit his chakra into the bodies and control them remotely as if they were his own, while bestowing each with certain abilities that Nagato wielded thanks to his Rinnegan. The many animals summoned through the Animal Path technique also had a number of these body piercings, suggesting that Nagato controlled them in a similar manner. When using the Summoning: Demonic Statue of the Outer Path, several of these receivers were pierced into Nagato's back in order to allow him to transfer his chakra to the statue and in doing so, manipulate it.

During the course of the Fourth Shinobi World War, Tobi utilised these same rods to control his own Six Paths of Pain comprised entirely from reincarnated jinchūriki, using only one receiver per body. By using them to manifest chakra chains, he was able to maintain authority over even the tailed beasts sealed within the jinchūriki, while retaining a connection between the beasts and the Demonic Statue.

Chakra Disruption Blade
These chakra disruption blades are the bladed versions of the chakra receivers. Nagato was able to store and extend the blades as needed from both arms of any Path, at various length. Pain can also detach the blade from the arms when requiring to use several of them, or to be thrown as spears.

These blades disrupt the chakra of its victim, impeding their movements. When a victim is stabbed by the blades, the Rinnegan appears in their mind. These blades are very sharp, as they were able to pierce the skin of Sage Mode users. Though the blades are made from durable material, they can be broken with enough force. However, due to being made of the same material as the chakra receivers are, they are durable enough to wear down metal blades such as scalpels without any trouble. Not only that, these blades are strong enough to deflect Blaze Release: Susanoo Kagutsuchi arrows despite them being made of Amaterasu.

Nagato, due to being immobile, can fire his chakra disruption blades from his mechanical seat, which then allows him to control the victims like one of the paths due to the close proximity between each other. Naruto was able to resist Nagato's influence with the help of both Sage Mode and the Nine-Tails chakra.

Chakra Receiver Stakes
These stakes greatly differ in size and design. However, not unlike the other variations, the user is capable of channeling their chakra through it. During the Fourth Shinobi World War, Obito Uchiha employed these against Naruto Uzumaki and Killer B. He keeps them stored in another dimension, and readily deployed them when desired. When applied with enough force, they can pierce the flesh of fully transformed tailed beasts. Also like the simpler chakra receiver, the user can channel their chakra into the stakes to manifest chakra chains, with which he is capable of binding the powers of a tailed beast.

Trivia

 * The main difference between the simple chakra receivers and their bladed version, is that the receivers begin transmitting chakra to his Six Paths of Pain when they are activated. Nagato also seemingly went to some lengths to retrieve them. These on the other hand, are used in battle and only transmits chakra when Nagato wants.
 * In the anime, the chakra receivers are shown to have a red reflection.
 * It has been shown that the receivers inserted in the revived jinchūriki move position when they go through a transformation and get bigger. As seen with Rōshi, he transformed into Son Gokū's full form. It moved from the chest, up to its neck.