Knob screw. Models: FS 260 FS 260 C-E FS 261 FS 261 C-E FS 360 C-EM FS 410 C-EM FS 361 C-EM FS 411 C-EM FS 461 C-EM FS 460 C-EM FS 460 C-EM L FS 460 FS 490 C-EM FS 491 C-EM FS 510 C-EM FS 560 C-EM FS 561 C-EM