Flexible Coupling - NinjaFlex/ABS Dual Print

Print it in Ninjaflex at 70mm/s with the [Flexion Extruder](https://www.flexionextruder.com "Flexible filament extruder")

This is a bellows-style flexible coupling with ABS hubs and NinjaFlex bellows. I printed it on a Replicator 1 with this extruder upgrade: http://www.thingiverse.com/thing:169086. The difficult part about dual extrusion (especially with flexible materials) is dealing with the material that leaks out of the idle printhead while the other is extruding. To get around this