From the Knit Picks Website:
Make this adorable dress for a very special little girl! A challenging project that will please the intarsia lovers, but well worth the effort! Sizes from 3/6 months to 10/12!

Sizes:
3-6 months - 20” chest
12 months - 21” chest
18 months - 22” chest
2T - 23” chest
3T - 4T - 24”-25” chest
5T - 6 - 26”-27” chest
6x - 7/8 - 28”-29” chest
10-12 - 29”-30” chest

Needles:
Size 3 (3.25mm): 24” circular
Size 2 (3.0mm): DPNs