Spread it over the crotch and either side of the groin next to the scrotum. It will disappear
gradually and for longer rides a reapplication at 40-80 mile intervals is a good idea. Like sun
screen it goes away. My experience is that it is needed if you get skin irritation in the groin or
crotch, not otherwise. I have also found that there are shorts and there are shorts. For me
the PI microsensor/ultrasensor are well worth the $100 +/- they cost for longer rides. The stuff
seems to wash out of the shorts ok. FWIW a look at the ingredients is useful, if water is listed
in the first 3 ingredients the stuff is going to go away faster than if no water at all is listed.
Your skin supplies all the water needed.