Hi Rjaedel
Igus bushings are plastic bushings manufactured by a company called Igus. Metal bearings have lubricant inside them. This lubricant is drawn out when the bearings start to rotate, forming a thin film over the ball bearings. The greater the speed, higher the lubrication. Hence at slower speeds the lubrication is not effective. In the case of plastic bushings, they are manufactured using thermoplastics, which have a solid lubricant embedded inside them. When the movement starts, the lubricant is released, thereby lowering the friction. Since the material utilized is plastic, the bushings are resistant to corrosion and are resistant to higher forces exerted on them. With regards to best bushings, plastic bushings are definitely more silent than the metal ones.