These days, instead of cardboard circles, there are actual pom-pom makers.
These pom pom makers are amazing little tools, and are a must have accessory, for any knitting or crochet fanatic.
This set is really easy to use and comes in 4 different diameter sizes: (3.8cm), (4.8cm), (6.8cm) and (8.8cm).
Diameter XL = 8.8cm (3.5 inches)
Diameter L = 6.8cm (2.7 inches)
Diameter M = 4.8cm (1.9 inches)
Diameter S = 3.8cm (1.5 inches)
Instructions for use are included on the reverse of the pack.