The Iron Age saw an expansion in the use of fibulae. The rounded bow fibula underwent several variations and were usually highly decorated with incised or moulded geometric designs. In one variation, the foot of the fibula that had previously terminated at the end of the arch with a simple catch plate, lengthened significantly. These extended foot fibulae, such as the Kahn type and the Pauken type, were found in the 7th to 5th centuries BC. The first long, bilateral springs appeared on some of these variants in the Hallstatt D2 era (5th century BC). These fibulae, such as the Doublezier type, looked similar to the Roman-era crossbow fibulae but were not the latter's direct precursor.