Gainsborough Short Outlet Pipe/PRD (Pressure Relief Device)

What size pressure relief pipe do i need for the 9.5kw se shower please?

Which size do I need for a Gainsborough 9.5 gse?

hi what size are the long and short versions? looks like the one in my shower but i cant judge it from the photos?

How can I order the long version, part no - 482804??