Can't speak for all OEM filters but a few years ago Kawi switched the part number on the OEM filter for my bike. I just happen to have one of each on the shelf and i compared them. The weight of the new one was several ounces less and looking at the inside the bypass valve was plastic where the old one was metal. Once i used both of them I opened them up and noticed there was less filter media in the new ones and i appeared to be thinner. This is also when I noticed the old one said made in Japan on it and the new one said made in china. That is when I switched to the K&N then after the news of the leaks were out I switched to the WIX. Also good info to have is that the Napa Gold filters as well as the Orileys Microguards are just rebranded WIX filters and are the same.