I'm used to replace the old down pipes 2 " with this one 4 " . Now I don't have any more problems with my bath to drain.
They do what they say on the tin. Only issue i had is that i managed to crack one and no i didn't use an impact driver but they were cold. Perhaps better to have used a washer or a pan head screw rather than countersunk
It's just a hopper, shoppers!
Needed to get rid of large amounts of roof water perfect for it