I have used Vittoria Pit Stop for many years with great success. I purchased a new pair of Vittoria Corsa Pro Tubular tires a few months ago for an important race in early August.I mounted the tires in mid July and one of them showed a slow leak. I ordered Pit Stop thinking perhaps I had somehow pinched the tire during installation. I have been riding/racing tubulars for over 60 years, mostly Vittorias. I used Pit Stop and it seemed to work until I did a test ride. The tire was flat within a few miles. I tried the second can with better success and so took the suspect tire to my race. The day before the race I did a recon on the course and that is when I discovered the leak was from the base of the valve stem. Fortunately, I had brought an older Vittoria Corsa, Graphene 2.0 and a tube of Vittoria Mastec in my kit. I ended up changing the tire in my hotel room the night before the race. I love Vittoria Pit Stop but it can't fix everything.