We have never really stocked any Tanaka heads other than a few Brains if people want them. The past few days we had to pull a couple of 5" semi auto heads off new machines because we had customers in need. So we ordered a few of them and they come with this white plastic spacer and a silver washer that the instructions say are to be used with Tanaka units....however I have never assembled a new out of the box Tanaka that had these parts. Is this something new or? Even the pair of 2501's that I sold yesterday did not have them between the head and the gearbox. Are these maybe for non tanaka products...some bad translation from Japanese to English or???