VEVOR Linear Guide Rail Set, SBR20 1000mm, 2 PCS 39.4 in/1000 mm SBR20 Guide Rails and 4 PCS SBR20UU Slide Blocks, Linear Rails and Bearings Kit for Automated Machines DIY Project CNC Router Machines

I would suppose you could use them outdoors, at least for a while. The mounting brackets on the rails are aluminum but the rails them selves appear to be chromed steel. The bearing bodies are aluminum and have plastic parts to retain the ball bearings that are inside. Personally, I wouldn't leave them out in the weather.

Yes, mine are outside. They are coated to avoid rust.

I don’t really know. The rail base is aluminum and the rail looks to be stainless steel but may just be a chrome plated steel. You may be applying some sort of rust inhibitor on a regular basis.

Probably not, it is carbon steel and therefore could rust. I use my indoors (garage) where it is not exposed to the weather. I have no experience with it outdoors.

I'm Sure They Will Rust Not Recommended

I wouldn't they're steel.