The V-Gauge includes a dial that will tell you when the proper vacuum seal has been reached. Just put the wine stopper into the neck of your bottle and use the included stainless vacuum pump to start pumping out the air. As you pump, watch the gauge until the needle reaches the "red zone". Once it's there, you know your bottle is fully sealed. And days later, when you're ready to finish the bottle, check the gauge to make sure that your wine is still preserved.