Sta-Kon RB4-EU BLUE POLYCBNT INSUL RING TERMINAL

The RB4-EU takes 1.5 to 2.5 mm conductor, which is the 16 to 14 AWG range in US sizing. Anything thinner than 1.5 mm won't hold a reliable crimp in this barrel, and 12 AWG will not seat, so step up to a yellow-coded terminal for that.

Blue is the standard color code for terminals sized to the middle wire range, and on the RB4-EU it corresponds to 1.5 to 2.5 mm conductor. Crews use it to sort terminals by wire size on a panel build without reading the stamp on each one, so keeping to the color convention matters if an inspector or the next electrician is tracing your work.

The conductive barrel and ring are electrolytic copper, with a polycarbonate insulating sleeve over the barrel. Copper keeps the resistance of the joint low, and the polycarbonate sleeve is a harder, higher temperature plastic than the soft vinyl used on economy terminals, so it holds its shape under a crimp tool and in warm enclosures.

Use the ring style, as on the Sta-Kon RB4-EU, wherever the connection is subject to vibration or where a loose screw must not release the wire. The ring is a closed loop, so the stud or screw has to come all the way out before the conductor can escape. A fork terminal slides out sideways and is only worth it when you need to service the connection often and cannot fully back the screw out. For motor terminals, ground studs, and panel grounding bars, ring is the right call.

Use a ratcheting crimp tool sized for insulated terminals in the 1.5 to 2.5 mm range. Pliers deform the copper barrel unevenly and crack the polycarbonate sleeve, which gives you a high resistance joint that heats under load. Strip to the barrel length only, with no bare copper showing past the sleeve.

Country of origin on the RB4-EU is Sweden. That matters on public and institutional jobs where procurement has to document sourcing on the submittal.