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 leave to amateurs