Filament Guide pivots freely on a skate bearing to ensure a straight and smooth filament path. Works very well and eliminates the "click, click, CLUNK" of the filament getting caught on the spool as with the oem guide. It runs smoothly and silently, less drag too. r2 of the axle just added an embossed arrow to show the direction of filament travel (axle is not symmetrical, there is a top and a bottom).This guide mounts exactly the same way as the factory part and has the same wire channel. Carefully press the axle into the bearing, then press the bearing into the Guide Support. The bearing is a standard #608 skate bearing: 22mm O.D. 8mm I.D. 7mm wide