New (less) flexible filament from the makers of Ninjaflex. Should improve printability.
http://www.adafruit.com/blog/2014/12/30/new-product-semiflex-1-75mm-diameter-midnight-black-0-5kg
It definitely does. I have a spool and love it.
And how well does it work in a Bowden extruder?
I only have one flex material, but a simple mod made it print very reliably. Line / sleeve the filament path with PTFE tubing so it doesn’t have room to escape or bind, and minimize all gaps in the path, the top end of the tube form fitting with the pulleys on top. I went from regularly jamming 45 minutes into a part without retractions, to retracting with impunity and never jamming again.