I found a new A/C system sealer about 2 months ago. This stuff seems to be working out very well. It travels with the oil instead of the refrigerant so there is no chance of contamination. In addition, since it is a two can application it can't plug the port like some of these products do. Instead of it being a "goo: it is in liquid form and because you have to be able to draw and hold a 24" vacuum for five minutes you know whether the product will correct the pinhole leaks before you install it. Simple - Effective.