B-Line Eaton series Flextray wire basket tray, Stainless steel, Protects cable from debris and dust, 2" X 118" flextray covers

The cover is steel with a stainless steel finish, and the model designation calls out 316 stainless. That's why it's recommended for high corrosive environments such as wash-down areas, coastal sites, water treatment and food processing, where painted or plain zinc covers will bloom rust.

Open basket tray is fine electrically; the cover is about what falls into the tray. It shields the cable from debris and dust, which is what you want under a ceiling grid being worked on, in a plenum above a kitchen, in a dusty industrial bay, or anywhere housekeeping and inspection matter. If the run is in a clean, dedicated cable space with nothing above it, many installs skip covers. Covering also gives a data or security run a physical barrier against casual access.

Material thickness is .074 inch. That's a light-gauge sheet, so it is a shield against dust and falling debris rather than a walkable or load-bearing surface. Don't plan on it taking foot traffic or stacked material.

Practically none. The cover is listed at .038 lb, so adding cover over a run changes almost nothing on your hanger or trapeze calculations. Cable weight remains the governing load.