Anyone have any experience with Fernco's waxless toilet seals? Do
they work as well as promised?

Here's my dilema. The outlet on the bottom on my toilet meaures 3
inches, and the inside of the flange in the floor measures what
appears to be 3 1/2 to 3 3/4. (I probably have some leftover "gunk"
from the old wax seal to chip away at...???) Either way, it's bigger
than a 3 inch hole, and smaller than a 4. Fernco makes a 3 inch
seal...a 4 inch seal...and what they call a "combination" - that fits
a 4 inch toilet to a 3 inch flange.

If I use the 3 inch, will I get a good seal in the flange?