This set is ideal for easily replacing either lost or broken watchband spring bars on any watch size. Made from stainless steel. The curved bars range in length from 10 mm to 20 mm (in 2 mm increments). The straight bars range from 9 mm to 20 mm (in 1 mm increments). This assortment set includes 300 assorted bars, along with a clear organizer box for easy and convenient storage.