Sta-Kon RC1157M INSVIN FRK TRM 12-10 No10 YEL MYLAR

The RC1157M is sized for 12-10 AWG stranded wire, which is what the yellow insulation signals on standard color-coded terminals. If you're terminating 16-14 AWG, you need a blue-coded terminal instead; 22-16 AWG takes red. Crimping a 14 AWG conductor into this yellow barrel will not give you a reliable mechanical hold.

Yes. The RC1157M carries UL file E9809, which is the Sta-Kon listing reference stated for this terminal. That matters on inspected commercial and institutional work where terminations have to be a listed component.

A fork terminal like the RC1157M is the choice when you want to service the connection without removing the screw, since the open tongue slides out sideways. A ring terminal is captive, so it can't vibrate off a loosened screw, and that's the one to spec for vibration-prone or safety-critical connections. Both are made in the same 12-10 AWG yellow range for No. 10 hardware.

The manufacturer part number is RC1157M, a Sta-Kon vinyl insulated fork terminal, yellow, 12-10 AWG, for No. 10 screws, with a Mylar-lined barrel. Made in the United States.

Vinyl, with a Mylar-lined barrel. The Mylar sleeve inside the vinyl keeps the insulation from splitting or being pushed back when the barrel is crimped, so the wire stays covered right up to the crimp. Vinyl insulation is for general-purpose indoor and panel work, not for high-heat locations where nylon insulated terminals are specified.

Yes, use an insulated-terminal crimper with the yellow 12-10 AWG nest. The color-coded die positions on a standard insulated crimp tool line up with the terminal's color, and the yellow station applies the right compression for this barrel without cutting through the vinyl. A bare-terminal or non-insulated die will crush the insulation and the Mylar liner.