Sta-Kon RB4F BLUE POLYCARB INSUL FORK TERMINAL

The RB4F is sized for 1.5 to 2.5 mm2 conductors, which is the 16 to 14 AWG range in North American wire. Anything thinner than 1.5 mm2 will not grip properly in the barrel, and 4 mm2 (12 AWG) is too large for it.

Yes. Blue is the standard colour code for the mid-size range of insulated terminals, and on the RB4F it corresponds to 1.5 to 2.5 mm2 (roughly 16 to 14 AWG). Red covers the smaller range below it and yellow the larger one above, so the colour is a quick way to confirm you have the right barrel size on a panel build before you crimp.

A fork (spade) terminal like the RB4F slides in under a screw or terminal-block clamp that is already in place, so you can land or remove a wire without pulling the screw all the way out. A ring terminal is the captive choice: the screw passes through it, so vibration or a loosening screw cannot throw the wire off. Use the fork where access is tight and service time matters, and a ring on motor terminals, grounds, and anything subject to vibration.

The conductor barrel is electrolytic copper, which is what gives it the low-resistance joint and the ductility to form around stranded wire. Crimp it with an insulated-terminal crimper matched to the blue 1.5-2.5 mm2 range, not with pliers; a ratcheting insulated-barrel tool set to the blue die is what produces a repeatable crimp on this size.

Neither. The RB4F uses a polycarbonate insulating sleeve, which is a rigid thermoplastic rather than the soft PVC found on cheaper vinyl-insulated terminals. In practice that means it resists splitting at the crimp and holds its shape better than vinyl when terminals are packed tightly side by side in a panel.

The RB4F is a Sta-Kon terminal, manufacturer part number RB4F, produced in Sweden. That matters on government, institutional, and utility work where country of origin has to be documented on the submittal.