We used this seat for our two children from about 10 months to 3 years of age. Rated up to 22 kg so can last longer than that.
Seatpost mounted - mount included. I might have some shims around to help fit your bike if necessary.
It's been in storage in the loft. You may wish to use the liner to make a new cushion.
Child bike seat (New Marston OX3)
This offer has been gifted to someone and is no longer available.