PLA worked for me. Polypropylene (PP) also seems like a good candidate for this, since it can be sterilised if needed and it flexes easily and won't wear out from deformation (since it's used for living hinges and such). The 11x clip 3MF file: It takes just under two hours to print 11 of these clips with a 0.8 mm print core, so 11 minutes each! The 4x clip dual color 3MF file: It takes 1 hours and 5 minutes to print this with 0.8 mm (black base) and 0.4 mm print cores (red heart).