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Plastron on a  unit.

Plastron on a protocol droid unit.

A plastron was the name of the broad piece of material covering the ventral (belly) side of upright, bipedal droids. It functioned as a protective covering for their internal circuitry and components. Bollux the BLX labor droid was fitted with an airtight, hinged plastron, in which was housed the slicer droid, Blue Max.

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