Can someone tell me the difference between the D020 and the D020--D?
D020 has 10 slits around a showerhead. The D020-D is slightly larger and has a matrix perc which provides more diffusion than the original D020.
If you're looking at the D020-D, I suggest you consider the GB-187 or the GB-187-S from Yingmin5 - it's a similar piece, but better build quality in my opinion. (Although Sunshinestore and Yingmin5 are both two of my favorite vendors on DHgate currently)