Flex - Fitz, McCoy, Montgomery, McLaurin

Current lineup
qb - goff
rb1 - bell
rb2 - mixon
wr1 - kupp
wr2 - edelman
te - ertz
flex - tbd

I have Fitz, McCoy, Montgomery, Mclaurin, and Tate on my bench. Need some help deciding who to throw in my flex