I needed some ballast tubes for a project of my own and so I've got a box full. ID is 20mm to fit the standard ballast used in most models I know of and 40cm long gives over 1.5kg of ballast capacity. From F3F to EPP these tubes will do the job!
I never have enjoyed making my own tubes and at £10 for a Factory built one it's just not worth it. The quality of the tubes is top draw and certainly above anything I canmake myself.
Drop me a line if you want one.