For what its worth... Ive recently had a handful of Teravail tubes fail, Very prematurely. The last one only lasted a couple days. My tire size is 700 x 42c. Ive been getting the Teravail tube size "700 x 30-43" from a local bike shop, so it should supposedly fit. Have had multiple failures. Most are small split seams on the inside of the tube - where it rests against the rim tape. My rim tape is good, and there are no sharp edges; I always closely inspect the rim right where the blowout happened, and always find nothing out of the ordinary there. I don't know if this company *always made lousy products, or if its just a slump/production problem they're going through right now, but these are crap. Stay away, unless you really like changing flat tubes for no reason at all.