The hosel depth difference is the main thing that could effect the length. The head size might contribute as well as the PTM is a slightly larger profile. That being said, I just took a 5 iron in each model and dry fit a shaft in each to see what the difference was in length. There was no difference. There can be slight tolerance differences in bore depths from set to set and head to head, but at least on the two heads I just pulled from stock and measured, there was no difference. Those tolerances should be not more than 1/32″ – 1/64″, if they exist at all.