Retrieval Nodes are like the opposite of Transfer Nodes; instead of pushing, it pulls.

It searches along Transfer Pipes, and then brings whatever it finds to its buffer, before pushing from its buffer into the block it's placed on.

Upgrades

An Item Filter or Fluid Filter can be installed into the respective Retrieval Nodes to limit what is allowed to enter their buffers.

Speed Upgrades will increase the amount of times Retrieval Nodes do work each tick.

Stack Upgrades increase the amount inserted into the buffer.