**Kenworth trucks made in March 2001 must check their existing hub adapter to determine which one to order. Adapter T04 has 40 splines with 1 single brass contact ring for the horn. If the existing hub adapter has 36 splines with 2 separate brass contact rings for the horn, you need adapter T03 instead, so you will need to let us know which you need.
Should you have any questions, do not hesitate to contact us. We are here to help!