This didn't used to be an issue but it can be troublesome today:
What kind of rims does your bike have? If it has a big valve hole, you need a SV tube. If it has a skinny valve hole, you need a PV tube. The valves come in different lengths too, too short is troublesome, too long looks goofy.
Good luck.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.