Sta-Kon RCC21 INSUL NYLON BUTT SPLICE 12-10 AWG

The RCC21 is sized for 12-10 AWG copper conductors on both ends. It's a straight butt splice, so it joins two wires end to end within that same 12-10 range. For 16-14 AWG or 22-18 AWG runs you need the smaller barrel sizes, not this one, since an undersized conductor in a 12-10 barrel won't crimp reliably.

Yes. The RCC21 nylon insulated butt splice carries a 600 V rating, which covers 120, 208, 240, 277 and 480 V building and motor branch circuits.

It is covered under UL file E9809. For an inspector or a spec that calls for listed wire connectors, that file number is what you cite. The splice is also made in the United States, which matters if the job carries a domestic sourcing requirement.

Yellow is the standard color code for a 12-10 AWG barrel in insulated terminals, and the RCC21 is yellow. On a job where you're pulling from a bin, the color tells you the wire range at a glance: red is 22-18, blue is 16-14, yellow is 12-10.

The nylon insulation on the RCC21 is rated to 105 C, so it handles the ambient inside RTU control compartments, ballast channels, and boiler room junction boxes. That's above the 90 C rating of THHN insulation it's typically splicing, so the splice is not the limiting element.

Use a controlled-cycle insulated terminal crimper matched to the 12-10 AWG yellow die station. Pliers or a generic stripper crimp will deform the nylon sleeve without fully compressing the copper barrel, and that's the connection that fails later under vibration. The RCC21 is a copper barrel inside nylon, so the barrel needs to be indented properly for a mechanically sound joint.

Nylon, like the RCC21, is the tougher choice where the splice gets pulled through a raceway, flexed, or sits in heat; it resists abrasion and cut-through better than vinyl and this one is rated to 105 C. Vinyl insulated splices are the lower-cost option for clean, static indoor terminations at lower temperatures. If the splice will be exposed to moisture, neither is right by itself, you want a heat-shrink adhesive-lined splice instead.

No. The barrel is copper and the splice is specified for 12-10 AWG copper wire. Aluminum requires a connector listed AL/CU with the appropriate inhibitor compound; putting aluminum in a copper-only barrel creates a galvanic failure point.

There is one configuration: model RCC21, yellow nylon, 12-10 AWG. No handing, length, or finish choice to make. If your run calls for a different conductor range, that's a different Sta-Kon part number rather than an option on this one.