The only problem with the Durabak and Herculiner is they are air dry not a chemical reaction. This means that over a few months they will dull from UV rays. If you try to wash either of theses two products wuth a was mit you will leave half the wool on the mit behind on the surface. I speak from expreiance. They seem to work prety good for the money I have used them several times. Sem makes a spray on that is activated. It dosn't dull and the surface is closer to that of a drop in liner. you can also get a tintable version of the Sem, you mix a urathane paint with it of your color chioce. you will need a racker shutz gun and a compresor for the Sem.