Its the same diameter on the inside, its just a thicker cover on the outside. I use to run them and now I'm running the black rubber fuel lines from NAPA. It last for along time just like the automotive fuel lines.
There is a 1/2" OD fuel line with the 1/4" ID.......but the more common "Big Line" used in karting is 7/16" OD
We carried both along with the standard 3/8" OD line most common to karting, but are phasing out the 1/2" OD stuff due to the popularity of 7/16"
The latest formulation of Oregon fuel line doesn't seem to last as long with the newer blends of pump gas we are seeing in the Midwest. The Excelon Brand of Fuel and Oil line seems to be lasting longer aand is a better value.