It is printed right on the side of the hose, 4.2mm. You get what you pay for and sometimes you don't even get that. I have had nothing but problems with Elring engine seals and wildcat vacuum line. Sure the stuff will last long enough to get out of the 1 year unlimited warranty that I offer but it has been my experience that by the end of 2 years that the seals are leaking again and by the end of 3-4 years the vacuum line is shot. Yes, the factory Volvo seals and $20.00 a meter hose is more expensive but at least you are getting what you paid for. I for one would not want to go to all of the hassle of putting in front engine seals on a white engine only to have them leak again inside of two years. The vacuum line and rubber elbows that Volvo sells have a hard enough time standing up to the underhood conditions I would think that something aftermarket would be even worse. I would love to have someone prove me wrong though as better parts are always a good thing.

Mark