John Deere prints their part number onto the belts to eliminate confusion. You simply check if the number on the belt matches the part number sticker on the cardboard holder. You don't have to measure the belt. This thread is a mess of clickbait posts, exhausting and confusing with all the talk of aftermarket and shorter belts and adding brackets. I'll get some hate for that comment, but after reading all this, I'd want to throw the thing off a cliff out of sheer frustration. Haha. If the OEM belt isn't working, there is a reason, and your local dealership is your best resource for a machine that new. If there is a known issue, Deere has a whole department called CCMS (used to be DTAC) that the dealer can use to contact Deere engineers to figure out the problem. I'd search the database myself, but I don't work at the dealership anymore, but I can affirm that M158130 fits both serial ranges of snowblowers for the E120 tractor.