I used herculiner (sp?), and then put on two coats of enamel to fill the crevices. I was not impressed with the liner, it holds mud and dirt like mad. I have also wore through the liner where my heel rests. It is nice to just pull the plug and wash it out. When I was running in the snow and mud, I just left the plugs out. Didn't seem to pick up much from the underside, just from my boots,