question re presta valves

As I've already posted, I changed my first flat tire today, and noticed that the presta valve on the new tube is considerably shorter than the valve on the first tube. What's that all about?

Also, what's the point of the little ring that screws onto the valve and sits at the rim? Is that to keep the valve from getting pushed down when I inflate it or check the pressure?

thx!

The nut keeps the tube from moving around because the hole diameter is bigger than stem. You probably bought a tube for an aero rim which is taller than a regular rim.

Veronica

thx Veronica. I learned a lot about tires this weekend!