When looking at the 5402FE series of cables from Belden, you may sometimes find some part numbers with the suffix “U”. The datasheet does not call out a meaning for this suffix.
Suffix “U” calls out a pull box, as opposed to a spool as below figures.
Applicable part numbers
5402FE 008U500
5402FE 008U1000
BEL1347-500-ND
BEL8286-1000-ND