To block off the opening after moving the BOOM audio plug outside of the saddlebag to allow for tank/compressor clearance. 2-piece unit allows you slide around the wire loom without cutting any wires. Normally only used on 2014-2020 cvo models, or models with BOOM audio added to the bike. Priced each. Each can be used on either the left or right side. Basic rear just requires (1) spacer, but fast rear or front+rear would require (2) spacers. Includes mounting hardware to attach to saddlebag.