When a facia mount needs to stand off the surface it bolts to, this spacer sets the gap. It adds standoff distance behind the bracket to keep 316 stainless off bare concrete and cut moisture and corrosion, to take up the slack against an uneven stair stringer face, and to hit a setback the edge rail calls for. It also opens up clearance for tools during install. It's 316-grade satin stainless steel for marine-grade chloride resistance outdoors and in humid air. One spacer fits across all the facia mounts, working with every OD, both.060".080" wall tubing, and both the standard bracket and the bottom-support version.