Two reasons many of the OEM’s still use .355 in many of their models. It is one less cut they have to do in production, so it does save time. Technically, the .355″ taper tips shafts are constant weight. When you use a .370″ parallel tip shaft blank and trim it for the flex and club head number, the shafts progressively get lighter the more you cut. The majority of players will not be able to tell the difference, but most tour players can and they prefer taper tip. Most likely because that is what they have always used, but the constant weight factor is part of it. OEM’s will use .370″paralle tip shaft in some models. More than you think, but most of the “players” models will usually have .355″ discrete length taper tip, constant weight shafts. There are .370″ discrete length constant weight shafts available form Nippon. They make all their .370″ options in discrete lengths and constant weight, just like their .355 taper tip options. From my many years in the business and making clubs for all levels of players, and even in some blind testing we have done over the years, the vast majority of players would not be able to tell the difference in the a .370″ version shaft form a .355″ version that are the same model and flex. From an inventory keeping standpoint, it is definitely easier to have .370″ parallel tip shafts than .355″ discrete length taper tip shafts.