y piece dimensions please

[rburnham11]

Does anyone know the dimensions of the standard y piece? ie the size of the v bands, the actual y pipe size and I know that the bottom bit of the y piece slides inside a 3 inch pipe but I dont know the exact size of it. Lots of you have probably got a spare y piece in the garage ready to swap on come mot time, if so would one of you very kind guys have a quick measure up for me please????