The yarn used was Stylecraft Lullaby Double Knitting yarn with a tension of 22 sts and 39 rows to 10cm, over half fishermans rib stitch, using 3.75mm needles, or the size needed to give the right tension.
The yarn is in 50 g balls and you will need 2 balls for the 12" and 14". 3 balls for the 16" and 18" and 4 balls for the 20" and 22" chest.