Abstract: A punch unit allows an adjustable length adjustment of the punch by disengaging projection-seat means which connect the housing and the guide bushing and then rotating the guide bushing relative to the housing. Additionally, the housing has mutually engaging housing top and bottom parts that have engaging fingers and corresponding grooves that cooperate during punching. The connection between the housing and guide bushing includes a C-ring, attached to the housing, having protrusions which are biased to engage a groove located on the guide bushing.