Forgotten Realms 4: The Magister, the fourth supplement of the Forgotten Realms series.
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FR-4 (aka FR4), is a widely accepted international grade designation for fiberglass reinforced epoxy laminates that are Flame Retardant (self extinguishing).
FR4 |
This is done through various substrates, both rigid and flexible, most commonly FR4 for rigid, and polyimide for flexible.