I am a newbie so I purchased some 1.75 mm Polymakr filament material. It could not push out the 3.00 mm stuff that was left in the nozzle, so I had to disassemble the head & clean everything. When I got it back together it still would not feed. I went back to the ABS for now, but I need something that will not shrink. The Polymakr stuff says it has little shrinkage & it comes in 3.0 mm. So I will try to find some of the larger stuff. What bothers me is that after I cleaned the head, I manually tried to shove the 1.75 mm up the tube while I manually heated the head to 250 DegC & it still would not come out of the nozzle.