Yes, the clear one in the sample pack you sent me was very brittle, to the point it would break under extruder pressure inside my bowden cable (got a Huxley).
I solved it by doubling the length of the bowden tube (greater arc => less flexing).
Apart from that it is a very good product - oh yes also it tends to warp a little printing big parts, but I'll retest that once all my temperature settings are done.
Didn't have a chance to test the other colors yet.
