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Structural MK (Upgrade)
The Structural MK is an item added by the JABBA mod. An upgrade used on a Better Barrel. It must be installed in sequence from I to VII. Each upgrade increases the capacity of upgrade slots to receive upgrades such as the Storage upgrade. Make sure you crafted your fences according to the vanilla recipe. Fences crafted through the Extra Trees recipe can not be used at this time. To install an upgrade, shift-right-click on the barrel with it.
Structural MK (Upgrade) has no known uses in crafting.