1 inch bulkhead is too big?

[ReefPup]

I purchased a pf-300 hob overflow and the specs say it has a 1 inch bulkhead. I ordered a 1 inch female to barbed to connect vinyl tubing. However the bulkhead is too big to fit the 1inch female to barbed adapter. Am I stupid or does the pf-300 have a larger bulkhead than what is on the specs?

 

[ReefPup]

Nvm I just did more research and learned that you have to glue pvc to the inside not screw something on.