Found out a particular line produced by Taulman and it's 1.7mm round Nylon 6. You can tell by the mesh on the roll and how they hold the start of line with a rubber band just like their 3d printing filament. Also an Amazon reviewer stated they called and verified with the reseller. Excited to give it a go but need to print a tool to help spool some to new proper sized rolls. If it runs well $40 for 5lbs is a steal at $8/lb.
I've attached my profile that I've been using for this trimmer line. I've set filament size to 1.70mm you just need to adjust your nozzle size and anything else you want.
5lb/2.2kg Spool: https://www.amazon.com/gp/product/B01E13CQ7Q
3lb/1.4kg Spool: https://www.amazon.com/gp/product/B003VPAEL6