These are the various components for replacement parts / spares.
Knuckle: This 8" knuckle has gear grooves on all 4 sides of it giving you up to 32" of gear groove. You can mount this in various places on your boat to maximize your "track components" in one location. (does not come with mounting hardware)
Gusset Pack: This is the mounting hardware to mount the knuckle to the backing plates (plates not included)
Spacer Bar: This 29" anodized aluminum spacer bar features a gear groove spanning the entire length. Used to connect the knuckles on each side of your kayak for support. This can also be used as a 29" gear track anywhere you install it on your kayak.