Size of the front handle inner tube?

I’m going to be combining my front handle to the main body of my thrower soon & I’m opting for a “non-rotating” thing. I want to order the inner tube & want to confirm what the correct size is. Can anyone tell me the correct size in decimals (or however the on-line metal stores list them) for the inner front handle tube? I have a “freeky geeky” main body & front handle if that helps.