Masonry control joint rubber/pvc

[darthsoilsguy2]

i'm having trouble figuring out if there are reasons out there to specify one masonry control joint material over another one. i haven't dug very deep on this but what i have seen from manufacturers is this... we sell synthetic rubber CJs and they are good for "A" and "B"... or we sell pvc CJs and they are good for "A" and "B".

Any preferences out there worth sharing?

 

[JedClampett]

Some of them have better fire resistance than others, although I can't remember which.