PorcelQuick Grout Backer Rod is a flexible, compressible closed cell polyethylene foam cord, used to support grout in the open joints. As the space between Adpeds will be open the grout would fall through these gaps, so the Grout Backer Rod acts as a barrier, holding the grout in place during the installation and curing process. PorcelQuick Grout Backer Rod is available in 3 diameters; 6mm, 10mm & 13mm, and is sold by the metre.