Best monitor size for dual monitors to go with 27"

[braadles87]

I currently have a 27" samsung monitor and am looking at getting a second monitor to increase productivity, i dont want another 27" as that would be too large so ive been looking at 21-24". I just wanted peoples opinions on dual monitors in general and the best size to go alongside a 27". Thanks

 

[smayekar912]

18.5" is Good for Second monitor