Taulman PCTPE Filament 2.85mm X 1lb
One of the six great materials from the Taulman Kickstarter campaign from Fall 2014. While the campaign didnt meet its ambitious goals, Taulman was able to leverage the support they had received into funds for production. So, I guess Kickstarters loss is your gain.
PCTPE (try saying that 3 times fast) stands for Plasticized Copolyamide ThermoPlastic Elastomer.
It is a more flexible elastic nylon than bridge, 645, or 618.
Its elastic modulus is around half that of 618. This means its about twice as flexible.
It also has a 370% elongation to break.
Printing temperature is around 230C and it can be printed on a slightly warm (40C is recommended) print bed coated with PVA (glue stick or brushed on dilute wood glue).
While it is very flexible, it is still stiff enough to feed easily through any extruder without special modifications.
This consists of 1 lb of filament on the standard Taulman Spool.