There's no such animal, in any brand. If they're DL, then they'd be 2.4x (at a guess). If they're 16x, they're single layer.
I agree with Arachne and geno888: best to steer clear of Memorex. I actually have some Memorex 8x hub printable DVD-R's that I bought when I wanted hub printables and nothing else was available (it was Boxing Day). These ones are made by CMC; they don't burn very well in my old Pioneer burner, but work very well in my new one. Even so, I won't be buying them again. (I can get Verbatim hub printables cheaper.... when the store's open.)
So what sort of burner is it? Some handle various grades of media better than others.
EDIT: Beaten by Qyngali.