You are looking at a Pro-tek brite-dip anodized aluminum swing arm spool kit that screws directly into the underside of the swing-arm on a 2003-2008 Kawasaki Z1000 models.
This Kawasaki 10mm spool kit is
made from 6061 T6 billet aluminum, is brite-dip anodized in five colors (Silver, Black, Red, Blue and Gold) and comes with all Black Oxide coated bolts needed for screw-on installation.
This Kawasaki spool measures 45mm (1 3/4") in length and is 25mm (1") in width. It takes a 10mm x 1.25mm x 50mm 12.9 alloy steel bolt that is countersunk into the spool.
Certain colors are limited so don't sleep on this great deal.