Walking Foot Even Feed made by Alphasew #10449T

Why this walking foot and not one of the others?  The opening for the needle is more than a single circular hole.  It is open from side to side so that if you were able to do a zigzag, the needle would be able to go side to side.  The advantage of this is that there are some of the Featherweights that were adjusted/made so that the needle is slightly one side or the other of absolute middle.  Have not seen it often, but have seen it, so decided to add this walking foot for those that need it.