Characteristics
Overview
Armor or clothing compatible with insert slots will roll an additional slot when crafted using this upgrade.
The point is room for one more insert. Its text says that armour or clothing compatible with insert slots rolls an additional slot when crafted with this upgrade, so each kit your group makes at that bench can hold more than it otherwise would.
That matters most to players who craft armour and lose it often: the PvP group that kits up every evening, the roamers who contest monuments. Say your team is heading for Launch Site. With a spare slot, a piece could carry a metal insert for the gunfight and a lead one for the radiation. A farmer who wears the same kit for days gets far less out of it.
Watch out
The slot is rolled when the piece is crafted. Armour you already own, or take from a crate or a dead player, stays as it is, so craft the kit at the upgraded bench and not at a spare one somewhere else in the base.
You will not craft one yourself. The row lists 100 metal fragments and 200 scrap at a Level 2 workbench, but the game files say the upgrade cannot be crafted or researched at all, so it comes from loot or a trade. Recycling a spare gives back part of the fragments and none of the scrap.
Recycling
At power grid stage 2 a green recycler works at 60% instead of 50%. Yields depend on the recycler.