well with strip u need to not smoke for 2 days prior if u read the directions..i know many who use it for probation and it is not a blocker like almost all other drinks it reallly cleans u out....some counceling places test for blockers (how ifailed my first time)...if iwoulda used strip i woulda passed i use it for probation and it works everytime..u just gotta READ THE INSTRUCTIONS!!!!