Tube Valve Length
Tubes come with several different valve lengths to accommodate different wheel profiles. Most bicycle wheels will work fine with 32mm valve lengths, but higher-end bicycles are often equipped with "aero" wheels which having a higher rim profile necessitating a longer valve stem. You should have enough valve sticking through the rim to easily attach your pump. With most pumps and inflators, about a half inch will do the trick. If you think you might have a problem with the shorter valve length, using a longer valve tube will not cause any real problems. The only real downsides are increased aerodynamic drag and weight (both of which are pretty minimal) and aesthetics.
If you have a very deep rim profile, even the longest valve stems may not be adequate. For these cases, we sell valve extenders which screw onto the standard Presta valve to add additional length.