That is very low, is it a solitaire? I would not go below 6.5mm for a solitaire. I would worry about the culet touching the metal or sticking into my finger.

The lower the better, in my humble opinion!!!

Like Poppyseed said, as long as the culet is not touching anything, you can have it as low as you want. My OEC moissy and my oval diamond both have bezels that sit that low. In fact I think my oval diamond is even lower than 4mm. However, not sure what the depth is on a 2ct (8mm) OEC, but I think it's deeper than 4.2mm. What kind of mounting is it?!?!

It is a solitaire with side stones. I guess I will see how it turns out and make adjustments from there. It is interesting how varied these responses are. Lol.

Yeah, but with prongs or bezel? You can usually go a lot lower with a bezel.

Oops! I guess that would be important. It is prong set with 4 prongs.

You can print a paper milimeter ruler here

It's very accurate. I use it for everything!

I love low set! It's totally personal preference.

Okay, I may be wrong here, but I would think that the 8mm (2ct) OEC is deeper than 4.2mm. If you're buying your setting from someone other than the person who is mounting the stone, I would check first to make sure it's going to fit. It sounds like a real tight fit to me.........

The depth measurement on an 8mm oec should be at approx 4.8mm minimum. Nicely proportioned OEC's have a depth of 60-65%.

That's what I thought!

My 9mm OEC moissanite has a depth of just under 6mm's.