S Series vs KH Fork Differences

KH (top) vs S series (lower)

The KH lower fork is longer than the S series and the axle fitment spacing is different.
Wheel axle must match fork lower.  They are not interchangeable.
S series drain screw is centered on the tube and KH series is offset.
Caliper mount spacing is 72mm on both.

A complete list of S3 vs KH fork asm differences can be found here.

H2 Fork Asm

KH500

KH500 outer tubes are longer than earlier tubes and have drain screw offset from center.
Caliper mount spacing is wider on KH500 (72mm) than other H series (54mm).
KH500 uses the same inner tube as other H series.
All H2/A/B/C and H1B/C/D/E/F use the same inner and outer tubes although internals differ.