They are 3/4 inch female ports. The DI vessels from gapswater come like that.
You will need 2 x 3/4 inch screw in male fittings to attach your inlet and outlet hoses. You can get 3/4 inch to hozelok male type adaptors that are ideal for these.
If you get stuck I am sure we have some in.
They are cheap and i will be happy to pop a couple into a Jiffy bag and post them to you.
Cheers
Andrew