Probably the hardest bit was removing the old one, which had been pushed down too far into the pipe. The new one went in very easily after spraying the inside of the pipe and rubber seal with some silicone spray.
works ok would buy another
Small and easy to install, just slots straight into 4 inch pipe. Installed one 4 months ago and works like a dream.
I used this and extended the vertical pipe with 2" waste to get the valve 200mm above the waterline, very good quality and got rid of my soil pipe boxing in.
Worked straight away as required