Lawn Boy Mower Blade part# 612540 has a length of 21". The center hole on this blade has a diameter of 7/8". The two side mounting hole have a diameter of 3/8" and they are 3-3/4" apart on center. We were unable to find a list of mower models that use this blade. Please refer to a parts breakdown or an owners manual to assure that this is the correct part number for your model.