Not sure what exactly you may need but it includes a union. I've added their info and product page below. Side note the Cor 15 and 20 both do. I have three of them 2x 15's and a 20. Love the pumps. Pretty dang rock solid and built like a truck. The body is really well built.
Note from the page:
INCLUDED FITTINGS
The COR comes complete with all the fittings necessary for most aquarium configurations (0.75″ output, 1.0″ input). But we’ve also included a 1.25” union for the output so you can connect the pump in a manner that will result in the least amount of head loss. Plumb your main return-line in 1.25″ and get the full potential of the COR pump – as much as 50% or more flow!
Here is the product page:
https://www.neptunesystems.com/products/expansion-modules/cor-20/