need help replacing Tailpiece extention

[acas1207]

Thought this would be easy even for me. In my bathroom sink the tailpiece extention was punctured (it is a flexible plastic like a bendable straw). I bought a replacement and installed it the same way the old one was installed (I think). The bottom part of the extention fits snugly into the p-trap with a gasket and a nut and the top of the extention just slips over the tail piece (not snugly) and screws into the same kind of nut and gasket but there isn't really a seal. It's like the water just 'dumps' into this piece. I compared the new parts to the original and it looks like it's the same thing but the old one worked. What am I doing wrong?
Thanks,
Anthony

 

[phishfood]

My first guess is that the extension is 1 1/2" tubular, the drain on your lavatory is 1 1/4". There is a really thick washer that is used to make the transition in size from 1 1/4" to 1 1/2". If you use a washer meant to attach
1 1/2" together, it will not seal.

Does this help out?

 

[acas1207]

Yes. Those are the dimensions. I have tried the different gaskets in the kit always with the same result.