Full radius woodruff keys are a full half circle and make full contact with the shaft keyway. Full radius woodruff keys require precision of the seat groove as contact can occur between the woodruff key and the bottom of the seat causing interference and the key to protrude from the groove higher than desired.
Flat bottom woodruff keys have the same profile as standard woodruff keys, however, the bottom of the key has been shaved flat. The flat bottom reduces the potential of interference at the bottom of the seat, allowing the woodruff key to seat fully in the groove and alleviating potential clearance issues of excessive key height.
Hi‑Pro keys, also known as high-profile woodruff keys, are a variant of woodruff keys that feature a full radius but have the added feature of feet. When installed, the feet extend over the face of the host shaft, preventing the key from rocking in its rounded seat.