Molded joiner sleeve. Use to attach boom stock end to end. Useful to replace broken or lost factory part or for making that extra long fuse version you've been planning. Use glue to lock joint or drill and bolt in traditional fashion. Fasteners not included, part is un-drilled. Discontinued by Millennium R/C, sorry! See Millennium R/C X-Fuse Parts Spru for this part linked here: https://www.radicalrc.com/item/Millennium-RC-X-Fuse-Plastic-Parts-Spru-107009 SKU Number: RRCSSBMJNR