Great stuff!!! all my spider cracks were grinded out and filled with Duraglass. Once filled easy to sand then apply more if needed for deep grindes. Last step use a fine sandable fering putty, I used Americas Cup from Fiberglass Coatings tuff stuff will not shrink... Make sure when you sand, sand in a pattern using all points in a compus N to S, E to W, NE to SW, etc...