ATtiny841 SSUR or SSU

I order the ATtiny841 SSUR, then i noticed that there is also an ATtiny841 SSU, what could be the difference ?? i didnt find anything usefull in the datasheets.

The ATTINY841-SSU and ATTINY841-SSUR are exactly the same part, the “R” means the part comes on tape or reel.

Thanks David