SA2MH080G2K5 = 9.5mm 2.5" drive, 3.5" adapter bracket, screws, SATA signal and power cables, installation guide, and warranty documentation.
I believe the SA2MH080G2R5 might be drive only.
The drives themselves are exactly the same.
From what I can work out the SSDSA2MH080G2R5 is a cut down retail box of the SSDSA2MH080G2K5 where you get the following:
Includes installation kit that contains: 3.5" desktop drive bay adapter to 2.5" SSD adapter bracket, screws, installation guide, and warranty documentation
for SSDSA2MH080G2K5 you get as above but with:
SATA data cable, power cable and a speed demon sticker.
Since the K5 and R5 appear the same I could put my 2 K5's and My 1 R5 together in a RAID 0 and it would be fine? All mine are new retail and the boxes packing and drives with adapters appear the same. Thanks Steve