Size 6 = 5.6cm long
Size 8 = 6.5cm long
Size 10 = 7.3cm long
Size 12 = 7.5cm long
Size 14 = 8.2cm long
Size 16 = 9.3cm long

https://www.waltons.ie/home/products/view/08asch-406-schwarz-jaw-harp-size-6/