CERA-ROD is a round, flexible, continuous-length, non-absorbent, non-gassing, non-staining and non-shrinking material extruded from a cross-linked polyethylene. Compression/deflection is approximately eight psi. Works equally well with concrete or asphalt surfaces. Use with hot-applied joint sealants...will not melt, shrink, evaporate or stain. Retains its original diameter and is non-gassing when exposed to high sealant temperatures. Prevents run-out through voids or bottom of the joint...saves sealant material. Acts as a bond breaker to stop sealant adhesion to the bottom side of the joint. Fast and easy to apply.