STIHL uses a custom blend of polymers to provide a line with the best all around characteristics of abrasion resistance, flexibility over time and temperature ranges, and welding resistance.
Colour-coded by size:
Blue - .065 (1.7mm)
Green - .080 (2.0mm)
Orange - .095 (2.4mm)
Red - .105 (2.7mm)
Black - .130 (3.3mm)
Fits Models: FS55, 56, 90, 100RX, 110,A 250