The element is slightly taller and has the
most pleats, meaning more paper to filter better.
The compression coil spring is stronger
(I guess that is better?) and the mount seal
is wider then the HD (but slightly slimmer then the CC).
The metal end caps are of heavy metal.
This is a great filter. But I question where
it's made (it's made by Hi-Flo for K&N),
and what micron it is? K&N says it is made
to their specs, but not that it's USA made
(as their air filters are). Also, it has a
17mm nut attached (we all love that!),
to me the mm size suggests its off shore made.