As recommended by the manufacturer I use MacTac 9800 primarily in my PC-600. Realistically you can print on any vinyl as long as it's smooth and cleaned properly first (clean/wipe down before printing with 91% isoprpyl alcohol printing). I also print a lot on specialty films such as Coburm or R Tape Vinyl EFX, just as long as it has the smooth clear layer on top. Now for the bad news, white streaks, gaps or lines in the print are generally a clear indication of a bad/blown print head.