Mapei Mapeflex Blackfill - Verticle Flue

[Clint 1979]

Morning all, I'm fitting a verticle flue through a flat felt roof this week and have come across this stuff - http://www.mapei.com/public/BR/linedocument/pieghevole_mapeflex_blackfill_gb.pdf
Has anyone used this to seal the flue and flashing to the felt before? If so is it any good or would you recommend something else??

Many thanks for any advice,
Clint

 

[jonnyswamp]

Never used it, ring a roofer and have it done right