Oooh interesting question...my Elkay undermount is 18 gauge....back in 2004 I redid our kitchen with Corian (anyone remember that)
Anyway I selected the components for the hardware, and I went online for them. They were about half of today's prices. I wanted to go deeper but they recommended I didn't as it would need support from underneath. I don't know which of these models it was, but web says 18 gauge.
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I can say this, so many things have been dropped over the last 19 years, yet it still looks great and no dents. I just dropped a bowl the other day while washing and was annoyed with myself. When it was brand new, these girls came over and spent the weekend and cooked. I heard my Wusthofs among other things banging on the sink--it was like a Kohler commercial, I wanted them to leave temporarily, so I could check for scratches lol