The front tires on my Craftsman lawn tractor deflate after each use. Replaced tube 4 times and tire 3 times. Nothing works. Won't buy this again. Once the tire is flat I can inflate it - IF the stem doesn't fit the rim - then I have to call a technician to pull the valve stem out for me. They seem to do the trick - have used them twice already and they worked as they should. I wish I had bought them many years ago - it would have saved me a lot of time waiting for the mechanic.