A-H147109-AI Knife, RotaryOne New Aftermarket Replacement Rotary Knife Fits John Deere (Fits JD) 50 and 50A Series Row Crop Headers This aftermarket replacement rotary knife Fits John Deere 50 and 50A Series row crop headers. The rotating knife section works in conjunction with the stationary knife blade to cut crop stalks cleanly as they enter the header. Six knives are used per row. Installs using square head countersunk bolts (not included). Heat treated for extended wear