In 35mm, I'm an Olympus OM user, have been for many years and have a large variety of Olympus Zuiko lenses in the stable. I do however have a number of Tamron SP adaptall lenses and as any who have used them know, Tamron made some lens that performed as well, if not better, than some OEM lenses. One of the ones I own is the 17mm f3.5, model 51B . It is one of the few that I own, for which I don't have an OEM lens hood. In this case the 20FH hood. Recently started looking for one and and searched eBay listing without much success. The difference between my early model of the 17mm (51B) and the later model (151B) is the earlier mode had built in filters and didn't use plastic in its construction. Herein resides the question. All the 51B lenses I saw on eBay seemed to have Y2, 80B and 81B filters. My lens has Y2, R60 and 81B filters. I'm wondering when the change occurred and if the ones with the red filter are actually less common . Oh, and if anybody has a 20 FH lens they are willing to sell . . . . Bill Barber