Rust Manual

Workbench Upgrade (Medium)

3 possible drops, resolved through every nested sub-table down to real items.
Surplus Workbench UpgradeSurplus Workbench UpgradeFun1x33.3%
Reinforced Workbench UpgradeReinforced Workbench UpgradeFun1x33.3%
Efficiency Workbench UpgradeEfficiency Workbench UpgradeFun1x33.3%

Chance the item is included whenever this table rolls. Approximate — doesn't account for seasonal or event-restricted rotations.