According to Netcore Enterprises, their Fender Covers do not fall off, leave black marks or an oily film on the paint, cause scratches or prevent access to any part of the engine bay. They have slippery topsides, and backsides with enough friction to grip paint without sliding or scratching. Powerful permanent magnets are located inside an enclosed sheath at the top edge of the cover, which attaches to the vertical lip of the fender where the hood comes to rest when closed. With a shielding that prevents magnetic fields from affecting sensitive vehicle or instrumentation electronics, these magnets can also be repositioned to maneuver around rubber bumpers or bolt heads. Furthermore, some models incorporate hooks along the top edge to connect to non-metallic fenders or fenders in which there's no vertical lip to place the magnets. The company also says their covers are impervious to grease, oil, solvents and other common auto shop chemicals. These covers can be folded or hung up, and both sides wipe clean for easy maintenance.