With regards to graphite shafts, there still exists product that may be branded or co-branded for the OEM’s the same as the aftermarket, but is a modified design. Modifications are made for one simple reason, to reduce cost to the OEM. The product the OEM’s sell in their custom departments is, as far as I know, is the same as the aftermarket product. Example if you order a Graphite Design Tour AD DI in your new OEM driver it would be the same as we sell. However, if the shafts in the OEM drivers that are stock, on the shelf models, that are branded the same as an aftermarket product, it most likely is not the same. Hopefully that makes sense.
In steel, most are the same. You may see a model in an OEM that is a little different in it’s branding for the OEM, but is actually the same as an aftermarket version. For instance, you might see and XYZ 110 in a particular OEM iron that is stock, and it is the same as a XYZ 105, or 115 etc. that is sold in the aftermarket. There are some steel shafts that are branded specifically for the OEM’s and may be a model that is not exactly like the aftermarket. Just depends on the program and the quantity the OEM will commit to as to whether or not the shaft company will produce a unique steel shaft just for them. I have also seen an aftermarket product that is sold under one brand used in an OEM under a completely different name.
Important to understand that in most cases, especially with the major OEM’s, that they are using quality products in shafts. They are not going to spend millions of dollars to develop a high end, expensive to produce club head with a bunch of technology and then put a piece of junk shaft in it. Yes, specs may be modified to reduce costs and they may not be exactly the same as the aftermarket in some cases, but they test and know that the combination of head, shaft and grip they put in the market meets a quality level of performance that is required to maintain higher level of product integrity and acceptance by the market.