Real filament is an independent manufacturer of high quality filament, produced locally in The Netherlands with a specific emphasis on thermoplastic purity. There are no cost-saving "filler" additives that may impact performance or reliability. Real gives you consistent print conditions at a low price, making it amongst the highest value filaments on the market.
eSun is a Chinese manufacturer of quality 3D Printer filaments. They offer great value for a great price, with a broad assortment of products. With their years of experience in the field of filament production, you can be assured that the filament is consistent in quality and diameter unlike most cheaper filament manufacturers. So if you are looking for a usable cheap filament, please check out the products in this category.
NinjaTek produces high quality flexible (Ninjaflex) and semi-flexible (Semiflex) 3D printer filaments. The Ninjaflex filament is a rubber-like, elastic filament. It is a more advanced material taking more effort to understand and cannot be printed in a bowden system, but is very suitable for applications where a lot of flexibility is required. Cheetah is a bit less flexible and serves a different range of applications.
The ReprapWorld Brand contains high-value products for the best 3D print experience. Selected for the amateur and pro alike, these products will make your life easier.
E3D is a manufacturer of extruders with a well-known reputation in the Reprap DIY community.
Extrudr is a producer of high quality, professional Bio-friendly filament.