As a rule, we don't joke about tape measures,
(sorry) but more than
anything else, size matters most.
Oh sure color, style, finish, texture,
cost, warranty, etc. are all important too
but rare indeed is the job that doesn't
start with a measurement of some sort.
Many people think that all
building products come in standard sizes (most do)
only to realize that they should have
measured the old thing (whatever it is)
before they headed out for the
appliance store, hardware store or lumber yard.
You may get lucky and happen to find the
right thing without a problem,
but chances are that you would be better
off measuring carefully,
making a drawing of some sort and/or
taking a picture with an instant camera.
When in doubt you should call the place
where you are going to make your purchase and ask them what to
measure for.
If they are not willing to be helpful,
or do not know the answers right away,
DO NOT SHOP THERE,
your job is too important to trust to amateurs.