It is supposed to stop fogging inside the scope. (I believe) If it leaks out, I will send it to the company to have it refilled. But so far it hasn't and I don't expect it to. Buffalo hunters worked their trade when they wanted to. If the scope fogged up, they waited or dealt with it. They had all the time they needed. We don't. The match ends if you are not ready to shoot, and hunting season is during the colder part of the year where the rifle spends some of the time inside a warm truck.