Stinky I was told (3 times cause I kept not getting it)....it would prevent the formation of male flowers in a female plant and if....IF.....male flowers were to form on said plant after using reverse they would be sterile nanners. As far as I know that's all it does and said plant can get pollinated from another male. So far in my using it I have never gotten to the "if" stage (knock on wood) but I'm very careful when removing any normal males from my grow room......even with the reverse.