I've got the taller, thick walled milky white ones.Maybe post a picture for us?
When they released the R7, they went to a better, taller and thicker clear-ish white suction cup. I doubt the thinner black ones would hold an R7 for long. They may have used up their stock on the black cups and just consolidated part numbers to use the same cups from the R7 on the R1 and R3. That would make sense to me. The black ones were nothing to write home about.
I've been using the standard thin wall, short cups on my Escort Redline for around ten years. I can easily attach the unit to my windshield and more importantly I can easily remove it while parked. Attaching the thick cups Uniden mount to the windshield separately means leaving in on the window and removing the detector every time I park, then fumbling around trying to find the slot in the front of the detector and scratching the lens every time.