Foam-Filler is a lightweight and flexible filler for smoothing foam and other rough surfaces. It is used to fill “dings” or dents – its easily applied with a spatula, can be smoothed (or thinned) with water, and dries quickly. It can be very easily sanded. For larger holes applying several layers works best. The product remains flexible enough to avoid cracking (which can happen if you use regular spackle) which makes it excellent for use with foam, which is also slightly flexible.