Polymaker Fiberon Black PET-GF15 3D Printer Filament 3KG, 15% Glass Fiber Reinforced, High Strength & Heat Resistance, Ideal for Automotive, Industrial & Functional Parts, AMS Compatible

The most engineering-minded consumer brand in this space. Polylite is their everyday PLA, PolyMax adds impact resistance, and PolyWood nails the timber look. They publish data sheets and actually explain what's in their formulations.