This is an after market trimmer head for the Stihl Autocut25-2.
Part# 4002-710-2191
It fits the following STIHL trimmers
FS 55 R, 55 RT, 55, 80 R 80, 83R, 83 RT, 83, 85 R 85 RT 85,
90 90 R, 110 RX 110 R, 110 120 R, 120 200 R 200 250R, 250