It was a mystery, previous owner said he put a larger one in due to issues with collapsing the air intake hose when working hard. He said it was from the next size larger tractor. I figured out that the OEM number I need is MA-1031051120, which fits the 26 HP models. I just didn't want to spend the $150 +/- to find out it was wrong, and couldn't find any cross reference for it to verify dimensions. I ended up with a WIX 46496 which measured the same, just had to enlarge the hole for the wingnut and swap over the plastic fins. Now that I am certain of the correct one I may spend the $$ next time for OEM.
Thanks all for the help.