Black, white or red rectangular-shaped resin pieces screw into your cable ends to hold a current project while using the tips for another project. White [S] end stoppers fit onto Chiaogoo [S] coded TWIST™ & SPIN™ cables. Black [L] end stoppers fit onto all [L] coded TWIST™ & SPIN™ cables. Red end stoppers fit onto all TWIST™ MINI cables.