Printed a bunch of the different types of these in PLA, PETG, ABS Pro, ABS and so far they all work great. The ABS and ABS Pro feels the best and strongest and the slight flex in ABS works well. But they all work great and there's no problem connecting an ABS Polypanel to a PLA or PETG one. My 3 year old likes them and I see a use for them in my own projects as well. Great job.