Polymaker Fiberon PA6-GF Glass Fiber Nylon Filament Grey 3kg, Fiberon PA6-GF Nylon Warp Free 3D Printing Filament

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.