VEVOR 30 Amp Generator Cord and Power Inlet Box Kit, 25 FT, NEMA L14-30P/L14-30R STW 10 AWG Generator Power Extension Cord with Twist Lock Connector, Pre-Drilled Inlet Box for RV Outdoor, ETL Listed

This product is rated up to 50 Amps and it doesn’t matter what type of wire you connect to as long as it is within the specified writing

For a 50 amp circuit you use 4 AWG aluminum wire.

i would not use aluminum wire.

It's actually a soft metal insulated box

Yes it is and it the plugs are easily removed

Yes, the box is metal. The spring loaded cover and knockout covers are plastic.

yes it is and very well made

Actually it's a hard plastic.