i think you have that backwards! drop in’s get water under them and rust away. i’m not sure what due time is, 20 years? 30 years? i can tell you it’s not 5 years that’s what mine’s been on for. it’s seen the freezing cold temp’s of denver, it’s also been through a couple hurricanes,no rust yet best part i put stuff like groceries or tools and drive and when i get home or wherever it’s right where i left it no sliding around.
edit: to answer the where at question, pick your company line-x or rhino then go to the website. they both offer dealer in the south hills. just stay away from the color match it will fade in the sun