Harley-Davidson part number 42428-81 is a Rear Brake Pedal (foot brake lever).
Part Details & Fitment
This is an original equipment manufacturer (OEM) part typically used on late Shovelhead-era FX models. It appears on the "Rear Brake Control (Late 1979 and Later)" factory diagrams.
Common Model Fitment:
FXWG (Wide Glide)