Summary My second version direct drive extruder, I got the handedness incorrect for my mounting on my first one. This version has a funnel in the arm that you can fit a small sponge or cloth in to clean the filament as it goes in. I also curved the bearing end of the arm slightly to allow it to grip even tighter. If you use nylon filament and a good stiff spring it can drive curtains. Quietly. Parts: http://hobbyking.com/hobbyking/store/__10201__HK_500GT_Ball_Bearing_9_x_4_x_4mm_Align_part_H60103_.html ) 10mm fine pitch bowden clamp for tube for 4mm OD tube. ( http://www.robotdigg.com/product/348/Heavy-duty+push-fit+bowden+connector+4-01 ) Long direct drive 400 step per rev low voltage Nema 17. ( http://www.omc-stepperonline.com/9deg-nema-17-bipolar-stepper-44ncm623ozin-17hm191684s-p-12.html ) side mounted. Note that the bearing cavity has 0.75mm thick supports designed in that should be carefully removed first with sharp side cutters.