I thought about one of these as a work table. Being made for optical testing they are nearly dead flat, which really appeals to me. Usually have tapped holes in a precise pattern, might be great to bolt things down. The downside for a workbench would be they're hollow as mentioned, The holes are usually only 1/4" threads (a bit small for general shop use and mounting things) and the top surface is typically only 1/4" thick. I picture the threads getting gummed up with dust, small chips, etc. Ultimately decided it wouldn't be a good fit in my shop, but might be fine for a light table for "cleaner" operations than I do.