Inserter capacity bonus (research)
When inserters are moving from one Storage/Stack to another (or loading/unloading trains) they can move more items at the same time. It works only when moving from stack to stack. In other words: If either the target, or the source has no stack, the stack size bonus doesn't work. Which is in most cases when moving from or to a belt.
A slow inserter with stack size bonus of 4, which moves from chest to chest, can easily keep up with a fast inserter, moving from chest to a belt. This is also one reason, why it is a bad idea to move copper wires with the belts.
This bonus is is also often called "inserter bonus", "stacksize bonus" , "stack bonus", etc.
It is directly related to Logistic robot cargo.
|Technology:||Inserter item stack size|
|Requires:||Logistics 1 |-||Effects:||