I believe it’s 1 1/8; Here’s a photo of the crossover unit section. I like how they changed it without removing the crossover section per the photo album.
Here’s a link to that size hose although as mentioned before; it’s quite a bit longer. Just got this example and the partial part number from the album previously mentioned as well. Look right?
https://www.anythingtruck.com/product/292-5515125.html