I need to change out the schrader valve on the low side on my ac. I'm thinking about getting this tool to do so. I would like to do this so I don't have to expose the system to the outside environment as much as possible. Would this tool do this well or is there a better alternative. mastercool 81490. I've seen it for as low as 29$ and I figure that it would be an ok tool to have if it works as it should. Preferably I would like a tool that works with the gp and my s10. I think that the two systems are the same type but I figure it would mention that while I was at it. Thanks for the input guys.