Review on 🖼️ OOM 533212 French Cleat, Picture and Mirror Hanger, 60lb, Aluminum (7 Piece) - Enhanced for SEO by Morgan Gilmore

I need something to hang a fossil slab that weighs 40 pounds and looked perfect at it's 200 pound rating. I want it to be long enough to spread the load over most of the panel, but the length isn't listed in the description above, so I looked under 'Product Information' where I found 'Product Dimensions' which is are listed as 0.5. x 3.2 x 21 inches. Ideal. But not so much. When the spikes arrived I found they were not 21" but 18" - in a 21" package (see attached picture. I'm not an engineer so I can't judge the quality of the material and its thickness,