hopefully simple cat question

[taka21]

im getting ready to install a direct fit magnaflow catalytic converter on my 87 n/a
and im just wondering if there is anything special i might need to know before installing it
things like if the converter only flows in one direction or if the ring gaskets make a big difference
all info is greatly appreciated
thanks

[cuel]

ring gaskets keep it from leaking :) As far as direction, it should be marked in and out if it is directional. Check the instructions to be sure.

[taka21]

im just wondering why they are two different sizes